Jon Bazarsky, age 14, of Santa Rosa, Calif., for his question:
WHEN WAS THE AQUALUNG INVENTED?
Skindiving is the aquatic sport and occupation in which swimmers, using self contained breathing devices or dependent on their own their lung capacity, remain underwater for periods ranging from one minute to two hours. The aqualung, invented in 1943, was one of skin diving's most important advances.
Inventors of the aqualung were French scientists Jacques Cousteau and Emile Gagnan.
Self contained underwater breathing apparatus is usually referred to by the acronym as "scuba." And among the best known of scuba diving devices is Cousteau and Gagnan's aqualung, which consists of one or more tanks of compressed air, a system of valve mechanisms, an inhalation hose, an exhalation hose and a mouthpiece.
Swimmers equipped with an aquaiung and two tanks of compressed air can remain submerged for more than an hour. The record depth for a diver using such gear and breathing compressed air is 437 feet.
In experiments, divers breathing mixed gases, notably helium and oxygen, have gone to 2,000 feet and occasionally even deeper. Authorities warn, however, that amateur skin divers should stay about the 30 foot mark and should learn the sport only under expert guidance.
The most elementary form of artificial breathing apparatus for skin diving is the snorkel, a hollow plastic tube with a mouthpiece at one end and a simple valve opening at the other. By keeping the open end above the surface the skin diver can study the underwater scene indefinitely. Snorkels are rarely more than 15 inches long, as air cannot be drawn from the surface at greater depths.
The basic items of equipment for all forms of skin diving are a waterproof face mask and rubber fins or flippers worn on the feet. The face mask is designed to fit the contours of the face snugly. It has a shatterproof glass that affords clear underwater vision.
Rubber flippers on the feet enable the diver to swim underwater almost 50 percent faster than swimmers on the surface.
Other optional items of skin diving equipment include a long sharp knife, a weighted belt and depth gauge. The knife may be used, to free divers when their lines are entangled.
Many divers used weighted belts to control their buoyancy while underwater. The depth gauge, worn like a wristwatch, enables divers to check their distance from the surface.
In addition, many skindivers carry wood or metal spears with which they catch fish (the sport is called spearfishing) or which they use for self protection. The spears are used manually or are shot out of devices called spear guns and powered by rubber slings, metal springs, gunpower or compressed gas.
Skin diving received considerable impetus from the exploits during World War II of naval underwater demolition experts known as frogmen.
In recent years, skin diving has become a popular sport. Besides spearfishing, the favorite pastimes of skindivers include exploration of the ocean bottom, underwater photography and searching for sunken treasure.