Sharon Fisher, age it, of Memphis, Tenn., for her question:
WHEN DID DEEP SEA DIVING START?
First divers into the sea were breath holders who went deep into the Mediterranean Sea looking for shells as early as 4500 B.C. Ancient Greek and Roman divers also held their breaths as they looked for shells and pearls.
Early divers, of course, didn't stay under water too long nor did they go too deep.
Divers in the Persian Gulf used goggles made of polished clear tortoise shells as early as A.D. 1300. But these divers couldn't stay under water too long, either.
The first devices that allowed people to breathe under water were called diving bells. They were bell shaped hulls that were open to the water at the bottom and received air from the surface through a hose. Air pressure within the bell kept the water out of the device. Diving bells were used early in the 1800s.
Before that, in 1715, an English diver named John Lethbridge designed a leather and wooden diving suit that was used in salvage work. It didn't work too well.
But today's suits used for helmet diving are based on a suit introduced in 1837 by a German engineer living in England named Augustus Siebe.
By the late 1800s and early 1900s, the first independent breathing devises for diving appeared. The first safe and simple device, the aqualung, was invented only recently: in 1943 by two Frenchmen, Jacques Yves Cousteau, a naval officer, and Emile Gagnan, an engineer.
The development of enclosed diving tanks expanded the range of underwater activity. Otis Barton of the United States designed the bathysphere. In 1930, he and William Beebe, an American naturalist, made the first dive in it.
A Swiss physicist names Auguste Piccard designed the first bathyscaph in 1948.
Manned stations called underwater saturation habitats were developed during the 1960s. Buildings were erected on the ocean floor at depths ranging from 30 to more than 600 feet.
The first saturation habitat was built off the coast of France in 1962 by Cousteau. It allowed a diver to stay under water for weeks. He didn't have to leave his station daily but could stay under water for long periods of time without having to undergo decompression every day.
In 1960, the bathyscaph Trieste made the deepest dive ever recorded when it descended 35,800 feet into the Pacific Ocean.
There is greater pressure under water than on land. The pressure increases by almost half a pound per square inch for every foot of depth. Pressure on a diver 33 feet beneath the surface is twice as great as the air pressure at the surface.
During ascent, the pressure in the lungs must be kept equal to the decreasing water pressure. Otherwise, a serious condition called air embolism may result.