Adam Clark, age 10, of Santa Cruz, Calif., for his question:
WHEN DID DEEP SEA DIVING START?
First divers 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 breath as they looked for shells and pearls.
Early divers, of course, didn't stay under water .:~a$:~ long nor did they go down 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 in the early 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 10s, the first independent breathing devices for diving appeared. The first safe and simple device, the Aqua lung, was invented in 143 by two Frenchmen, Jacques Yves Cousteau, a naval officer, and Emile Gagan, an engineer.
The development of enclosed diving tanks expanded the range of underwater activity. Otis Barton of the U.S. designed the bathysphere, a round, watertight observation chamber lowered into the sea by cables. In 130, he and William Beebe, an American naturalist, made the first dive in it.
A Swiss physicist, Auguste Piccard, designed the first bathyscaph in 148, a deep sea diving apparatus for reaching depths up to almost seven miles without a cable.
In 160, the bathyscaph Trieste made the deepest dive ever recorded when it descended 35,800 feet into the Pacific Ocean.
Manned stations called underwater saturation habitats were developed during the 160s. 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 162 by Cousteau. It allowed a diver to stay under water for weeks. He could stay under water for long periods of time without having to undergo decompression every day.
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 life threatening condition called air embolism may result.