The aqualung, or scuba (Self-Contained Underwater Breathing Apparatus), was invented by the Frenchman, Commandant Jacques-Yves Cousteau during World War II. The aqualung enables a diver to stay underwater for long periods of time. This type of contraption eliminates the need for a divers suit, by distributing air at varying pressures during the dive.
The bodies of divers come under greater strain the deeper they go. The air in the diver's lungs is at a similar pressure to the surrounding water. The air within the cylinder is stored at high pressure. The aqualung consists of a regulator that has two stages. Reducing the pressure of the oxygen coming from the cylinder allows the diver to breath in.
The first stage of the valve, which works with the help of a spring, opens to admit air at a regulated pressure which is always greater than water pressure, this enables the diver to exhale. The second stage of the valve, which is worked by a lever, opens by suction allowing air in at water pressure and the diver is able to inhale.
