Australia Dive Training

Australia offers a wealth of travel experiences, from the drama of the outback and the diving spectacle of the Great Barrier Reef to the cosmopolitan city of Sydney and arguably the best beaches in the world.

Australia is an enormous country, and visitors expecting to see an opera in Sydney one night and meet Crocodile Dundee the next, followed by whale shark excursions in Western Australia the next, will have to radically re-think their grasp of geography and perspective of distance.

The detailed information about the courses is mainly related to dive courses in Australia. However, we can also arrange these courses for you at our other destinations.

Accreditations

A dive instructor will teach students according to standards of a dive association. There are a number of dive associations. Some of the biggest ones are PADI, NAUI, SSI and CMAS. They are all internationally recognized dive associations. If you have a certification card with one of them, you can dive anywhere in the world.

In Australia and most other countries in the South Pacific, PADI courses are most common. A limited number of dive operators offer NAUI courses, SSI courses and others.

Medical Preconditions

In Australia, it is required by law to take a medical examination before you take certain dive courses. If you are a certified diver (at any level) and just want to dive, you do not need to take a medical examination in Australia. more details on dive medicals

Definite contraindications to diving are:

• Diabetes I or II
• Asthma
• Pneumothorax (Scarred lung)
• Epilepsy
• Tuberculosis
• Heart diseases
• existing or assumed Pregnancy

Nikon D300 underwater photography

Nikon D300 underwater photography tests with sailfish

Sea & Sea released us an early version of their MDX-D300 underwater housing for the Nikon D300 just in time for my sailfish expedition on December 31, 2007. Personally, I was really hoping for their MDX-D3 housing for the NikonD3, but I was thrilled to have the opportunity to put the Nikon D300 and Sea & Sea MDX-D300 through a real world test.

Sailfish were a perfect test subject for the Nikon D300. These fish torpedoes require smooth camera pans and a shutter speeds of 1/250th to capture sharp frames. At such high shutter speeds, I was required to shoot at ISO 400 or greater to maintain apertures of f4 to F5.6. The new low noise CMOS sensor in the Nikon D300 was a perfect match. I brought my higher megapixel Nikon D2x as backup, but it never got wet. Our expedition was unlucky with weather, but the Nikon D300 and Sea & Sea MDX-D300 housing performed flawlessly.

ISO 400 settings very smooth
Blue light is the most challenging tone for all digital capture devices. Deep blue tones typically exhibit the most noise of any color channel. As with topside photographers that shoot at twilight, we underwater photographers are unfortunately pushing the limits of available digital technology. Based on my tests, D300 files shot at ISO 400 are as good or better than ISO 100 shots from the Nikon D200 and D2x. I was thrilled with the smooth gradients at ISO 400, but found noise creeping in at ISO 800. That being said, ISO 800 shots were on par with ISO 400 from previous Nikon cameras. My topside tests with the Nikon D3 have me confident that it will deliver even better high ISO performance. I can’t wait to get the D3 wet, but the D300 is clearly a significant leap forward for underwater photography in a low cost, compact Nikon SLR. I’m quite certain I’d never get film scans this clean at ISO 400.

Accuracy required with exposure settings
As with all digital cameras, you must shoot accurate exposures with the D300 to avoid the noise enhancing effects of brightening a dark image in post processing. Poor exposure at higher ISO settings is a significant penality. Use the RGB histogram to push your exposure setting as bright as possible without clipping highlight detail.

Avoid sharpening during Raw Conversions
Some people choose to apply a small amount (25%) of sharpening during raw conversion. I found that any amount of sharpening was detrimental to the smoothness of blue gradients during raw conversions and would highly recommend only selective (masked) sharpening on the final output file.

Australia Destinations Diving

Australia offers a wealth of travel experiences, from the drama of the outback and the diving spectacle of the Great Barrier Reef to the cosmopolitan city of Sydney and arguably the best beaches in the world.
Australia is an enormous country, and visitors expecting to see an opera in Sydney one night and meet Crocodile Dundee the next, followed by whale shark excursions in Western Australia the next, will have to radically re-think their grasp of geography and perspective of distance.

For example, Sydney to Cairns is approximately 2700 km (1700 miles), the same distance as Boston to Miami, or London to Athens. East to West is even further with Sydney to Perth being a 4 hour flight, similar to Los Angeles to New York, or London to Cairo.

Australia is big and it is empty. Only 19 million people live in an area the same size as the United States or half as big again as Europe. Most of these people live in a handful of coastal cities.

It is this sheer vastness, and the friction between the ancient land steeped in Aboriginal lore and the New World culture being heaped upon it, which gives Australia much of its character.

• Queensland
• Western Australia

MDX-D300 housing viewfinder options

MDX-D300 housing assembly, feel and finish
The Sea & Sea MDX-D300 has a very solid feel in the hand and its in water weight seems lighter than the Sea & Sea DX-D200 housing. Unlike the previous cast model, the MDX-D300 is milled from a solid block of aluminum and thus has a more rugged finish. It survived 2 weeks of very poor maintenance (fresh water rinses out of a gas can) and cleaned up easily with no signs of corrosion or fatigue. The quick lock camera tray makes camera installation easy, but when using a zoom lens, it's best to wiggle the zoom knob prior to locking down the tray to ensure a precise install.

MDX-D300 housing viewfinder options
Personally I find all stock viewfinders on underwater housings to be difficult if not impossible to use for accurate composition and focus verification. The stock viewfinder on the Sea & Sea MDX-D300 is no exception. I received the housing hours before departure and was unable to install the new Inon Straight (180) viewfinder and chose to use the Inon 45 viewfinder instead. The Inon 45 offers a bright crisp image with the largest angle of acceptance, but I found the 45 degree angle (head down) view to be difficult for the fast action of sailfish and dolphin. I brought the stock viewfinder along, but determined I'd rather have the large view of the Inon 45. I was able to adapt my technique over the period of a few days and would now like to travel with both the 45 and 180 viewfinders and swap based on my subjects.


MDX-D300 housing control ergonomics
The Sea & Sea DX-D300 housing features oversized knobs and buttons that are easily controlled with even gloved hands. Essential controls (shutter release, aperture, shutterspeed, and focus lock) are easily reached with a large hand, but small handed users will likely find essential controls more difficult with only one hand supporting the housing. The round and non-indexed knobs for MSC and AF-area Mode require practice to accurately adjust on the fly, but unlike myself, most users don't regularly access these controls. The unique barrel style control for the Sub Command Dial (aperture) is very convenient, but is half occluded by the Fisheye Dome Port when not using an extension ring. While I’m quite fond of the smoother controls and ergonomics of the Subal line of underwater housings, I was able to operate all controls on the MDX-D300 quickly within 15 minutes of the first dive. The last Sea & Sea housing I personally shot was their Nikon F5 underwater housing and it was a personal favorite. This new line of MDX housings is a great step back to their previous attention to detail. Hat’s off to the new design team at Sea & Sea!

Australia Dive Master Rescue

Cairns is one of the most popular places in the world where people learn to dive during their holiday. Dive schools in Cairns usually have regular open water classes with many students.

For those who want to become dive professionals, it is the ideal place to learn how to teach diving as there are so many students learning each day. Safety comes first. But also quality and efficiency are to be learned here. To assist an instructor in a large open water class prepares you well for "the real life" out there.

Taking a divemaster course in Cairns is a great way to gain experience. Also, it is a good base if you wish to continue to an instructor course. Most courses offered in Cairns are PADI courses. The course is at least 18 days long, but plan for 21 days, to be on the safe side. Part of the course is to assist an instructor in teaching 2 Open Water courses. When available you may also assist in Advanced and Rescue courses.

You get 2 live aboard dive trips (each 3 days/2 nights long) to the Great Barrier Reef. During these trips you will get up to 20 dives. Some are training dives and some just recreational dives.

During the course you get familiar with the diver training process and you will gain an awareness of typical student problems. Also you will learn how to supervise and control divers in general. You will learn to perform diving skills to demonstration level and, of course, you learn a lot of theory and take written exams. You need to be pretty fit too, as there are a few swimming tests.

Minimum requirements are:

• You should be at least 18 years old
• Have a PADI Rescue Diver certification
• A valid diving medical to Australian standard
  more details on dive medicals
• No less than 20 logged Scuba Dives when starting the Divemaster course, but to complete the PADI Divemaster certification you will need to have completed 60 logged Scuba Dives.
• Price for the 18-day Divemaster Course costs up to AU$ 1995 (until 31 March 2009). Please e-mail us if you are interested in this course.

THE OCEAN FLOOR

The ocean floor is home to many unique communities of plants and animals. Most of these marine ecosystems are near the water surface, such as the Great Barrier Reef, a 2,000-km-long coral formation off the northeastern coast of Australia. Coral reefs, like nearly all complex living communities, depend on solar energy for growth (photosynthesis). The sun's energy, however, penetrates at most only about 300 m below the surface of the water. The relatively shallow penetration of solar energy and the sinking of cold, subpolar water combine to make most of the deep ocean floor a frigid environment with few life forms.In 1977, scientists discovered hot springs at a depth of 2.5 km, on the Galapagos Rift (spreading ridge) off the coast of Ecuador. This exciting discovery was not really a surprise. Since the early 1970s, scientists had predicted that hot springs (geothermal vents) should be found at the active spreading centers along the mid-oceanic ridges, where magma, at temperatures over 1,000 °C, presumably was being erupted to form new oceanic crust. More exciting, because it was totally unexpected, was the discovery of abundant and unusual sea life -- giant tube worms, huge clams, and mussels -- that thrived around the hot springs.

tube

Temperature, Heat Capacity and Heat Conductivity

Temperature, Heat Capacity and Heat Conductivity The heat capacity of seawater is 3134 times greater than that of air. Water has insignificant heat conductivity. That is why distribution of heat to greater depths is very slow and is mainly achieved through convection.
The highest temperature of water is registered to occur between 3 and 4 p.m., and the lowest – a couple of hours after sunrise. There are three temperature layers of seawater: surface layer (epilymnion), intermediate layer (metalymnion), and deepest layer (hypolymnion). The thickness of the former two layers varies with the weather, season, and currents. The temperature of the surface layer is almost constant, being between 19 and 25ºC in the summer. As the deepest layer begins, temperature drops by a few more degrees and it remains constant thereafter (7–9ºC). That is the temperature of sea depths and it does not depend on the season.
Water Motion Water motion constitutes sea currents and waves. The reason for the formation of currents might be the different density of water, constant winds, etc. Ocean currents are usually caused by constant winds, whereas local ones are mainly due to the character of coastlines. According to he direction of their flow, currents can be classified as vertical or horizontal. There are three main types of waves: wind waves, standing waves, and seismic waves.
Wind is the main reason for the formation of waves. The process of wave formation can be divide into different stages. When the speed of wind is less than 1m/s, air motion does not affect the surface of the water. If wind intensifies, these rows of waves become irregular and peaks appear, which are due to the different pressure at the front and at the back of the wave. At a greater speed of wind large waves are formed, running in parallel rows. Th largest waves reaching hundreds of meters continue even when the wind has ceased. They create the so-called dead drift.
Standing waves are formed when the level of the water rises at one coast and in the same time drops at the other. A sudden decrease of atmospheric pressure at one of the coasts, appearance of strong wind or heavy rain can all be the causes for standing waves. The fluctuation of the sea level may reach 80cm, which is dangerous for vessels at the harbors.
Seismic waves are formed because of underwater earthquakes. A vessel that is nest the site of the earthquake experiences a hydraulic blow which is why old maps frequently contain non-existent reefs. Seismic waves are often present in the Hawaii region where they have the special name zunami. Such waves are formed in the Pacific Ocean, the Mediterranean, the Caribbean Sea, and the Malaya Archipelago as well. Sometimes, these waves reach the height of 35m and are dangerous not only for the ships but also for the native population because of their destructive power.Waves change their form when they reach shallow regions. When the depth becomes equal to the height of the wave, the water particles no longer move in a circle: their orbit becomes elliptical. The length of the waves decreases and the height increases. The front slope of the wave becomes vertical, the top is inclined forward, then it falls and eventually destroys the wave. This phenomenon is called a surf. Its force may reach up to 38 tonnes/m2.

DIVE SITES AROUND TO LOMBOK ISLAND (INDONESIA)

There are over 3,500 marine species living in the reefs and seas of Indonesia. In comparison to the Great Barrier Reef (1,500 species) and Red Sea (600 species), 25 % of all reefs in the world are in Indonesia.

The drop-offs, plateaus and slopes of the Gili's reflect a good cross-section of what Indonesia has to offer. Dive in and be fascinated by turtles, White-tip Reef Sharks, Cuttlefish, Moray Eels, Angel Fish, Ghost Pipefish and more.
Around the three Gili Island in the north-west of Lombok (Gili Air, Gili Meno, Gili Trawangan), are more then 15 different dive spots and there are new reefs being explored all the time.

Shark Point & Volkers' Golf Course

Shark Point, to the east of Gili Trawangan, is a popular dive spot in the mornings. This dive site consists of different levels (24m, 20m, 18m). It starts with a slope of hard and soft corals, the "native territory" of Green and Hawksbill Turtles.

The different levels are sandy areas with small coral locks - the variety of underwater life is large, starting with schools of Trevally Napoleon Fish to White-tip Reef Sharks and Rays in the sandy areas, ending up with Ribbon Eels, Leaf Fish and even Mantas.

Volkers' Golf Course is about 500 m east of Shark Point and starts at a depth of about 20m. It looks green like a golf course and is the best site to see Sharks, Schools of Mackerel and Doctor Fish. Because of its depth and the sometimes very strong currents, it is a dive for advanced divers.

Meno Wall

Meno wall, off the west coast of Gili Meno, goes down to depths of 18m. It offers a lot of small coral fish like Lionfish, Soldier Fish, Gobies, crabs, as well as Wart Slugs and Nudibranches coming out of hiding. It is also called "Turtle Heaven" because of the many resident Hawksbill and Green Turtles.

Air Wall

Air Wall, to the west of Gili Air, is a very beautiful wall that, due to the soft coral cover, shines yellow-orange depending on the position of the sun. The highlight of this wall is a coral block at 22m in which Leaf Fish (Scorpion Fish) make their "home", surrounded by shrimps, Pipe Fish, White-banded Cleaner Shrimps and thousands of Glass Fish. Look into the deeper parts for White-tip Reef Sharks.

Coral Fan Garden & Basket Coral Garden
Also popular for morning dives are the two dive spots in the north of Gili Trawangan: Coral Fun Garden and Basket Coral Garden. In the first few metres you have the feeling of being in an aquarium - schools of colored Fairy Basslets, Fusiliers, Banner Fish live here. Deeper, around the big coral and stone blocks, Groupers, Batfish, Trumpet Fish, hiding Octopus and Bearded Scorpion Fish. Look out to the blue: sometimes Eagle Rays, Mantas or Reef Sharks can be seen.

Manta Point

In the rainy season, when the water is rich with plankton, this dive site in the south of Gili Trawangan gives you the best chance to see Manta Rays. But even without the Mantas, you still have a good chance to see Reef Sharks and Turtles.

THE NATURE SEAWATER

Nowhere in nature can absolutely clear water be found. Even rainwater contains dissolved minerals. For example, 30kg of rainwater contains about 1g of solid substances, whereas 1kg of seawater contains about 35g different salts. Salinity is a very important characteristic and it directly influences the viability of the organisms living in the water. The total amount of dissolved salts in the oceans is 48 quadrillion tonnes. Most of it is NaCl (77.8%), to which the saline taste of seawater is due. Magnesium chloride accounts for 10.9% and it gives the water a specific bitterish taste. Then come sulfates (10.8%), carbonates (.5%), etc. The overall amount of salts may vary in different regions of the Ocean but the composition and the percentile content remain the same. The average ocean salinity is 35% and increases starting at the Equator and reaching 15–20º latitude, then it decreases towards the poles. This phenomenon can be explained with the distribution of water vapors and also with the saline waters transported from the tropical zones by warm currents. Salinity in the northern part of the Indian Ocean changes according to the season. Seas have greater salinity than oceans. The Dead Sea has the greatest salinity of all (256%), and the smallest is that of the Baltic Sea (5–7%).
The presence of more than 44 chemical elements has been established so far. Besides the popular oxygen, hydrogen, chlorine, potassium, magnesium, sulfur, calcium, and iodine, seawater also contains Al, Cu, Zn, Tn, Pb, Au, Ag, U, Mn, Hg, etc.
There are many gases dissolved in seawater, the largest amount being contributed by oxygen, nitrogen, and carbon dioxide. Water dissolves oxygen better than nitrogen. That is why the ratio N:O which is 4:1 on dry land, changes to 2:1 under water.

Scuba Diving in North Sulawesi

Gangga Diver's PADI "Gold Palm" Dive Center is run by International dive instructors. Qualified guides and dive masters pride themselves in offering very personalized diving service to suit and divers of all levels of experience. The dive center provides racks for each room to store equipment and has toilet and shower facilities with hot water- perfect for after those night dives.With its more than 30 world-class diving locations, the island offers a wonderful variety of marine life with rare species and pristine reefs. Gangga is the ideal starting point for diving the Bangka Archipelago, Bunaken National Marine Park (near Manado) and Lembeh Strait. During your stay, the dive guides will help you discover the marvelous underwater world and see the astonishingly rich variety of flora and fauna which delights underwater photographers. Scientists of marine biology from all over the world come to study and photograph the marine life found here.Gangga Divers has 5 all-wood boats specifically built for diving, three with onboard toilets, all with easy on and off access. The engine power ranges from 80 plus horsepower to 360 plus. The staff on the boats is trained to anticipate all your diving needs. Each boat is also full stocked with towels, freshwater tanks for cameras, drinking water, hot drinks and snacks.







Gangga Divers also has a regulator service room and three of the guides have diplomas for repairing and maintaining Scuba Pro and Aqualung regulators.Being a member of the North Sulawesi Watersports Association (NSWA), Gangga Island Resort is committed to protecting the local reefs and is involved in conservation and development projects aimed at helping the local communities create sustainable tourism activities.






Gangga and Bangka Archipelago
(click to enlarge) The small island of Gangga offers a unique opportunity to dive some of the finest Indo Pacific dive sites. Located at the conjunction of the Indian and Pacific Oceans, with more than 30 world class diving locations, the island offers a wonderful variety of marine life. It is perfectly situated to access both the North Sulawesi coast and other islands like Lihaga, Tindila, Talisei and Bangka.Click here for a few selected divesite descriptions of the Bangka/Gangga area.
Bunaken National Marine Park
(click to enlarge) This is a protected park of 75,265 hectares. In this area you find most of the species of coral fishes known to exist in Indonesia. There are more than 30 dive sites around five islands, including Montehage and Manado Tua. Because of its amazing visibility (20-30 meters), it is considered one of the best places in the world for diving. In 1997, a giant, prehistoric fish, the Coelacanth, which was thought to be extinct for more than 400 million years, was discovered here. Gangga Island is at a distance of 75 minutes from this diving paradise where you can dive with eagle rays, jackfish, tuna, sharks, turtles, napoleons, barracudas and so on.Click here for a few selected divesite descriptions of the Bunaken National Park.
Lembeh Strait
(click to enlarge) This area is a paradise for photographers owing to its 25 dive sites. It is widely known for its macro life. With an average of 10-20 meters of visibility, it is characterized by black, volcanic depths and its black sand slopes which highlight the amazing array of marine life. The Strait of Lembeh is famous amongst the best underwater photographers and organizations in the world because of the large selection of exotic, bizarre, and rare species. Gangga Island resort is approximately 75 minutes from this diving area. There you can discover pygmy seahorses, nudibranchs, giant frog-fish, Pegasus sea moth, Hairy Frog-fish, giant seahorses, cockatoo wasp-fish, leaf scorpion-fishes, many varieties of eels and more.Click here for a few selected divesite descriptions of the Lembeh Strait.

Blue Diving Club Gallery

EXOTIC BEACH GILI AIR LOMBOK INDONESIA

General Information
Gili Air is the nearest Gili to Lombok. It is also the most populated and you will find more trees there than the other Gili's. The local inhabitants are: Sasak, Mandar, Bugis and Makassar. You can find their unique culture that is different from Lombok and wonderful beaches. Many of the older generation still make their living as boatmen, fisherman and farming coconuts.

There are only a few number of 2 stars hotels (rooms with air conditioning, swimming pool, TV etc) on Gili Air. Most of places to stay are located in south, west and east side of the island. You can find many homestays or budget accommodation on this island. The island remains quiet and relaxing.
Most accommodations are locally owned and managed, while a few of the upmarket hotels own and managed by foreign investors. You can go from one island to another by joining the gili island's hoping boat (depart twice a day). People here are more friendly than on Gili Trawangan.
Activities
Snorkeling and diving are the highlight of the activities. Snorkeling area are located in the south east (opposite-facing the Lombok Golf Kosaido) and along to the north east). You can just jump into the water to see the colorful fishes and coral reef. In the western part of Gili Air you can't snorkel off the beaches. When the moon is high (low tide), you can't swim off the beach. You need to walk to the south or east side.
There are few quality scuba diving operations on all the islands.
While the island is busiest from May through August, the quieter off-season from January to April provides a better opportunity to enjoy all the islet has to offer, with accommodation prices at their lowest level.

To get around the isle, the only means of transport are Cidomos, horse drawn carriages. Bicycle rentals are available too. Expect higher prices for most things there since all food and goods must be brought over from the mainland.




BOOKING & ENQUIRIES
PT. LOMBOK NETWORK HOLIDAYS
Jl. Intermilan 85 - 87 Puri Meninting, Batulayar, Lombok-Indonesia
Ph: +62 370 6628139, Fax: +62 370 634 162
Mobile: +62 81 8369619
Email: info@lombok-network.com

Atmospheric And Hydrostatic Gas Presure

Atmospheric Pressure is produced by the weight of the gases in the atmosphere, acts on every body and in all directions. Its effects are therefore neutralized. At sea level, it equals 14.7 psi or 1.03 kg/cm2; larger values are often expressed in atmospheres. Atmospheric pressure decreases with the increase of height.
Hydrostatic Pressure is produced by the weight of a fluid, acts upon every body in the fluid, and is one and the same in all directions at a particular depth. Its increase rate is .445 psi/foot (1 kg/cm2 per 9.75 meters) when descending in seawter, whereas in fresh water it increases at .432 psi/foot (1 kg/cm2 per 10 meters).
Absolute Pressure = Atmospheric Pressure + Hydrostatic Pressure Its units of measurement are pounds per square inch absolute (psia) or kilograms per square centimeter absolute (kg/cm2 absolute).
Gauge Pressure is the difference between the absolute pressure and a specific pressure. It is measured with gauges that read zero at sea level. To convert to absolute pressure add 14.7 to the value in psi or 1.03 to the value in kg/cm2.
Partial Pressure is the fraction of the total pressure contributed by a gas in a mixture. It is in direct proportion to the volume percentage of the gas in the mixture.
The Buoyant Force is a very characteristic force that acts upon all submerged bodies. This is how Archimedes' Principle explains buoyancy:
A body immersed in a liquid, either wholly or partially, is buoyed up by a force equal to the weight of the liquid displaced by the body.
The following mathematical equation can be derived from Archimedes' Principle: the buoyancy of a submerged body = weight of displaced liquid – weight of the body. Therefore, we may conclude that:
1 The body will float if the buoyancy is positive (body weight < weight =" weight"> weight of displaced liquid).
The buoyant force of a liquid depends on its density, which equals its weight per unit volume.
The density of fresh water is 62.4 pounds per cubic foot (28.3 kg/ 0.03 m3).
Seawater, however, is denser: 64 pounds per cubic foot (29 kg/0.03 m3). A body immersed in seawater will, therefore, be buoyed up by a greater force than a body immersed in fresh water, so it is easier to float in seawater than in fresh water.
Lung capacity affects the buoyancy of a person. A diver with full lungs displaces a greater volume of water and, according to Archimedes' Principle, is more buoyant than a diver with deflated lungs. With full lungs, a diver’s relative weight is .96-.99; with deflated lungs: 1.021-1.097. Bone structure, bone weight and body fat are other factors that have an effect on buoyancy and vary from person to person. That is why some people float more easily than others.
Divers who wear wet suits often add diving weights to their weight belts to create the negative buoyancy needed for descent. At the desired depth, they adjust their buoyancy to an appropriate level so that work can be accomplished without extra physical efforts to oppose positive or negative buoyancy.
Usually, a person’s weight is slightly less than the weight of the displaced amount of water. For example, a person who weighs 80kg displaces 79dm2 of water, which weighs 79kg, that is, he has about 1kg of negative buoyancy. Balance under water depends on the location of the center of weight and that of buoyancy. If they are situated on a vertical line (the symmetry axis of the human body) and the center of buoyancy is higher than that of weight, equilibrium will be stable.
The relative weight of seawater is considered 1. That is why the loss of weight of submerged bodies in Newtons corresponds to the displaced volume in liters. The human body has a relative weight of about 1, which is why it weighs little under water . To ensure normal descent, it is not enough to regulate the weight of the diver. It is also necessary that the additional weights attached to the weight belt be situated so as to provide stable equilibrium, on condition that the equipment is intact.
All weight forces can be added and presented as a single force applied to the center of weight. Similarly, buoyant forces correspond to the center of buoyancy, located just above the center of weight. The distance between the two centers must be about 20cm. This fact allows the diver to maintain the erect position of his or her body.
If the belt weights are situated too high and the center of weight turns out to be above that of buoyancy, the diver will be rotated upside-down.
If the belt weights are situated too low, the center of weight would be much lower than that of buoyancy. As a result, the diver will be unable to bend or accomplish underwater work.

EXOTIC DIVE TOUR

SEAWATER fACTOR

Relative Weight
It is interesting to note that 1liter of air weighs .013N and 1liter of water weighs 10N, that is 770 times heavier than air. The relative weight of seawater depends on the density and temperature of the water. Density itself, though insignificantly, depends on temperature. That is why at 20ºC the density of the water is lower by .2% than it is at 4ºC. Pure distilled water has a relative weight of 1 at a temperature of 4ºC, that is, 1 cm3 of water weighs 1g. Seawater is heavier than fresh water by 2.5–3% because of the greater amount of salts dissolved in it; its relative weight is 1.025. It may be concluded that a diver weighs less in seawater than in fresh water. Relative weight is important for determining buoyancy.

Resistance

Just like any other liquid, water practically does not shrink. That is why its density almost does not change at different depths. At a pressure of 500at water shrinks by 1/47,000,000 of its volume. If it did not shrink at all, however, the sea level would rise by 30m. Water resistance is greatest in the surface layer. Therefore, less effort is needed for swimming in that layer.
Transparency The relative transparency of seawater is determined by the average depth, at which a white disc of a 30cm diameter is no longer seen. Greatest transparency has the Sargatian Sea (66.5m), second greatest transparency have the Syrian coasts of the Mediterranean Sea. Least transparent is the North Sea (the British Channel) – some 6.5–12m.
The heat capacity of seawater is 3134 times greater than that of air. Water has insignificant heat conductivity. That is why distribution of heat to greater depths is very slow and is mainly achieved through convection.
The highest temperature of water is registered to occur between 3 and 4 p.m., and the lowest – a couple of hours after sunrise. There are three temperature layers of seawater: surface layer (epilymnion), intermediate layer (metalymnion), and deepest layer (hypolymnion). The thickness of the former two layers varies with the weather, season, and currents. The temperature of the surface layer is almost constant, being between 19 and 25ºC in the summer. As the deepest layer begins, temperature drops by a few more degrees and it remains constant thereafter (7–9ºC). That is the temperature of sea depths and it does not depend on the season.

Water Motion

Water motion constitutes sea currents and waves. The reason for the formation of currents might be the different density of water, constant winds, etc. Ocean currents are usually caused by constant winds, whereas local ones are mainly due to the character of coastlines. According to he direction of their flow, currents can be classified as vertical or horizontal. There are three main types of waves: wind waves, standing waves, and seismic waves.

Wind

is the main reason for the formation of waves. The process of wave formation can be divide into different stages. When the speed of wind is less than 1m/s, air motion does not affect the surface of the water. If wind intensifies, these rows of waves become irregular and peaks appear, which are due to the different pressure at the front and at the back of the wave. At a greater speed of wind large waves are formed, running in parallel rows. Th largest waves reaching hundreds of meters continue even when the wind has ceased. They create the so-called dead drift.

Water and senses

Standing waves

are formed when the level of the water rises at one coast and in the same time drops at the other. A sudden decrease of atmospheric pressure at one of the coasts, appearance of strong wind or heavy rain can all be the causes for standing waves. The fluctuation of the sea level may reach 80cm, which is dangerous for vessels at the harbors.
Seismic waves are formed because of underwater earthquakes. A vessel that is nest the site of the earthquake experiences a hydraulic blow which is why old maps frequently contain non-existent reefs. Seismic waves are often present in the Hawaii region where they have the special name zunami. Such waves are formed in the Pacific Ocean, the Mediterranean, the Caribbean Sea, and the Malaya Archipelago as well. Sometimes, these waves reach the height of 35m and are dangerous not only for the ships but also for the native population because of their destructive power.
Waves change their form

when they reach shallow regions. When the depth becomes equal to the height of the wave, the water particles no longer move in a circle: their orbit becomes elliptical. The length of the waves decreases and the height increases. The front slope of the wave becomes vertical, the top is inclined forward, then it falls and eventually destroys the wave. This phenomenon is called a surf. Its force may reach up to 38 tonnes/m2.
Difficulties The change of water density, resulting from changes of temperature, salinity, and pressure has no practical importance to diving. Even though, water is a dense medium and creates significant difficulties for a diver’s movements. He or she cannot walk or turn as fast as in the air. While working under water, divers must choose positions and movements that create least resistance, e.g. walking sidewards being slightly bent forward. The use of tools is also hindered. For example, the use of a hammer is much more difficult under water than it is in the air. As a result, divers quickly get tired. That is why the work that is to be performed under water should be organized so as to facilitate the diver by minimizing unnecessary movements and providing possible help from the surface. Rapid currents additionally impede the accomplishment of underwater work. Mire, too, can create considerable difficulties for divers. Even the execution of simplest types of work becomes complicated and requires dexterity, resistance, and fitness. That is why rigorous physical preparation is crucial

Gas Presure Theory

First of all, we should point out that the pressure on a diver under water is the result of two separate forces which act simultaneously upon him or her. These are:

1. The weight of the water

2. The weight of the atmosphere over the surface of the water.
The table on the left provides mathematical equivalents necessary for converting barometric pressure units. The various types of pressure exerted upon divers are summarized further below. As atmospheric pressure increases, the height of the mercury in the tube also increases and vice versa. That is, the weight of the mercury in the tube always corresponds to the atmospheric pressure.
In the middle of the 17th century Italian scientist Evangelista Toricelli determined the value of normal atmospheric pressure with the following experiment. A mercury-filled glass tube with a section area of 1cm2 and a closed end was vertically immersed in a vessel full of mercury (Hg), the open end pointing downwards. The level of the mercury inside the tube decreased to a certain extent. Further decrease was impeded by the atmospheric pressure that acted upon the surface of the mercury in the vessel. It turned out that the mercury level in the tube measured 760mm and weighed 1033g. If water had been used instead, a different tube would be necessary. It would have to be longer as many times as water is lighter than air. The level of the water in the tube would correspond to the atmospheric pressure and would equal 10.33m. Therefore, at sea level air exerts a pressure of 1033g/cm2. Having in mind that the total area of the human body is 17,000–18,000cm2, it can be calculated that atmospheric air exerts upon us a pressure of 17 to 18 tonnes!
Scientists have proven that the critical point of the mechanical effect of hydrostatic pressure depends on the evolution level of the organisms. Lower unicellular organisms such as spores, bacteria, and viruses can withstand pressures of thousands of atmospheres. A further increase of pressure causes physical and chemical changes in the cellular structures, thus altering the characteristics of the species.
Divers do not feel the great pressure because the tissues of the human organism contain 65% of liquids that practically do not shrink. In inner cavities, the pressure of the inhaled air counteracts the external pressure. During descent, divers usually do not feel the increasing pressure. They only feel a slight difficulty while breathing because they inhale gases that are under a pressure equal to that of the surrounding water. All underwater diving suits ensure the intake of air held under a pressure that corresponds to the depth at which the diver is. Otherwise, the absence of this condition would cause quick death.
Although divers do not feel the pressure itself, its rapid change may lead to different sicknesses. A quick decrease of pressure during ascent is particularly dangerous and may result in a serious disease called decompression sickness. Read more on that in the Medicine Section.
While under water, a diver feels unequal pressure on the different parts of his or her body. Low parts, if in greater depths than the upper body, endure pressure that is greater by .15–.20x105 Pa than the one on the upper body.

DEEP_SEA DIVING GAS

A GAS used by deep-sea divers could help to treat severe asthma attacks. Tests showed the gas boosts lung function and speeds up recovery within an hour of being given.
French scientists who trialled the diving gas predict it could be a new emergency treatment for asthma sufferers who turn up at hospital in the throes of an attack. The therapy works because it contains a mixture of oxygen and helium. Normal air is made up of 20 per cent oxygen and nearly 80 per cent nitrogen.

Coral and Fish