Water Diving

1. Water Diving

2. INTRODUCTION Diving (underwater), act of entering water and remaining below the surface to explore, to work, or simply to have fun. Diving is popular all overthe world. It is usually done in the ocean,but divers also explore other bodies of water,including lakes, rivers,and ponds. Snorkeling on the surface(or just below) is a common form of diving, but many people use scuba, which stands for self-contained underwater breathing apparatus. Scuba divers carry a tank of air that allows them to breathe while deep underwater.

3. SPORT DIVING FUNDAMENTALS Because popular dive sites such as coral reefs and wrecks are typically not near land, most diving is done from boats. In some locations, however, divers can enter the water from shore. On a typical outing, the divers decide beforehand how long they will remain underwater and howdeep they will descend. While the divers are underwater, at least one person serves as a spotter by remaining on the boat or on shore. All groups, whether diving from aboat or from shore, are required to fly a diver down flag (a red flag with a white diagonal slash) to alert boaters that people are underwater Afterdivers put on their gear and double-check their equipment, they enter the water and descend. As they descend, the surrounding water pressure increases, causing a slight discomfort, or squeeze,in their ears and sinuses. Divers relieve this discomfort byholding their noses and blowing gently. This technique iscalled equalization, as it equalizes the pressure within the divers’ bodies with that of the surrounding water, allowing them to proceed safely.

4. Equipment Diving equipment depends on the location of the dive, but whether scuba diving or snorkeling, recreational divers need several basic items: a mask, a snorkel, fins, and, when necessary, an exposure suit to remain warm. Scuba divers wear special equipment to breathe underwater and to help control their position underwater.A diving mask that  covers the nose and eyes enables the diver to see while underwater.A snorkel is a tube that allows the diver to breathe while floating at the water’s surface.One end fits in the diver’s mouth and the other end extends above the water.Much like the flippers of a seal and the webbed feet of a duck, fins that are worn on the feet let divers propel themselves through the water with a smooth, energy-efficient motion.

5. Training and Certification Before taking a dive, enthusias ts must gain certification by passing a course offered by a certifying scuba diving agency. The largest agency worldwide is PADI, but there are many others, including the National Association of Underwater Instructor s and the National Association of Scu- ba Diving Schools These agencies sponsorcourses throughout the world, especially in places where diving is particularlypopular, such as the Carib- bean and Hawaii. All agencies require thatparticipants be proficient swimm- ers,in reasonably good health, and at least 12 years old.

6. Specialized Scuba Equipment To breathe underwater, scuba divers wear a metal tank filled with compressed air, and a regulator that attaches to the tank. The regulator reduces the pressure of the air to match the surrounding water pressure, so that the diver can breathe the air comfortably. The regulator also distributes the air among four hoses. One hose delivers air to a mouthpiece, through which the diver inhales and exhales. Another hose from the regulator attaches to an adjustable air bladder called a buoyancy compensator (or control) device (BCD or BC), which the diver wears as a vest. By adding air to the BCD, the diver becomes more buoyant and rises. By releasing air, the diver becomes less buoyant and sinks. With minor adjustments of air, the diver can achieve neutral buoyancy. A third hose attaches to pressure gauges that divers use to monitor how much air remains in the tank. A fourth hose attaches to a backup breathing device called an alternate air source, or octopus

7. Hazards and Safety Measures Hazards associated with recreational diving stem chiefly from breathing air under pressure, though a few marine animals also pose hazards. Most hazards can be avoided if divers follow the safety procedures taught in certification courses and do not attempt dives beyond their ability and experience.The single largest risk scuba divers face is pressure-related injury. Decompression sickness, also called the bends, is an injury that occurs when a diver ascends too quickly, or dives too deeply for too long. Throughout a dive, the body absorbs nitrogen (an element of air) from breathing compressed air. The deeper a diver descends, the denser the air that is breathed and the more nitrogen absorbed. This nitrogen forms tiny bubbles in the diver’s tissues and bloodstream. If a diver ascends to the surface too quickly, these bubbles remain trapped inside the body and can cause extreme pain in joints and organs. Severe cases of decompression sickness can be fatal. For this reason, all divers attempt to ascend slowly from every dive, to allow excess nitrogen to escape the body gradually. Divers who suspect they are suffering from decompression sickness should seek medical attention immediately.

8. Sport Diving Sites In general, divers seek locations where the water is clear, the temperatures warm, and the marine life plentiful. Divers often choose to visit areas with coral reefs because they are colorful and dense with life, and provide shelter for many types of fish. The Caribbean is the most popular destination in the world. Parts of the region are designated as marine parks or sanctuaries. Because they are protected from fishing and other human activity, these locations boast abundant aquatic plant and animal life. Similar protected areas exist throughout the world, and the South Pacific, the Indian Ocean, and the Red Sea are common dive destinations.

9. Related Activities As divers become more proficient, they usually want to take up related activities. Underwater photography and videography are the most common. Spearfishing, also called underwater hunting, is popular with some people. And divers can also choose specialized forms of diving.

10. OTHER PURPOSES OF UNDERWATER DIVING People who dive for recreation do so to enjoy aquatic life and observe the underwater world, but others carry out work underwater. Commercial divers are highly trained men and women who work on offshore oil rigs, pipelines, and barges, and inshore on civil engineering sites such as hydroelectric plants and harbors. At oil-drilling platforms, for example, they may perform such tasks as welding at depths below 200 ft (61 m). These tasks can require that they spend extended time underwater. Commercial divers use special equipment to stay underwater for long periods. Surface-supplied diving, also called hard-hat or helmet diving, affords commercial divers an unlimited air supply; a compressor connected to a surface reservoir provides the air to the diver’s mask or helmet through a long, flexible tube. The diver also wears bailout tanks in case of a malfunction with the air supply. The equipment used in hard-hat diving is cumbersome and hampers mobility, making it difficult to perform tasks with the arms, such as moving heavy equipment underwater

11. Submersibles Submersibles are pressurized vehicles that maintain surface air pressure inside while they descend deep into the ocean. The most common type of submersible is a submarine. Smaller submersibles are used in deep diving to transport hard-hat divers to and from workstations. Submersibles such as the bathyscaphe are used in deep-sea exploration, scientific studies, and military operations. Researchers continue to work on developing submersibles that could take scientists to the deepest parts of the ocean.

12. Living and Working Underwater In addition to commercial operations, other types of work are performed by divers with specialized training. Police divers perform search-and-recovery missions. Military divers engage in combat and surveillance. Treasure hunters and salvagers recover valuables by diving in areas where ships lie on the bottom. Marine biologists, geologists, and archaeologists use diving to gather valuable scientific information. Marine biologists collect data about plants and animals. Geologists learn about the formation of the earth by observing the insides of underwater caves and by studying the topography of the ocean floor. And nautical archaeologists find clues to history by surveying shipwrecks and sunken civilizations. Underwater Archaeology

13. Saturation Diving In some cases, commercial and scientific divers live in an underwater habitat, or pressurized chamber, for extended periods. In a type of diving called saturation diving, the diver’s body becomes saturated with gas mixtures corresponding to the working depth. Divers can therefore remain under a constant pressure for weeks or months, rather than go through a lengthy decompression during and after each dive. After early attempts in the 1950s, the first commercial application of saturation diving occurred in the 1960s on the Smith Mountain Dam project in Virginia. One of the most famous habitats was the Hydrolab of the National Oceanic and Atmospheric Administration (NOAA), which was based in the Bahamas and Caribbean from 1972 to 1985. During that time, Hydrolab was used by more than 600 researchers from nine countries. The  hazards  in  saturation diving are much like the hazards of living in a space station. Inhabitants depend on life support systems for their air and power supply. Should medical or mechanical difficulties occur, a risky evacuation procedure that requires a series of decompression stops is the only way to bring divers to the surface safely.

14. Source • Encarta Encyclopedia • Google Iviah Mariam Abraham VII – C Roll No: 31