and Emil Gagnan
to supply air to free-swimming underwater swimmer,
at the same pressure as the surrounding sea.
Jacques Cousteau told Gagnan exactly what he wanted. Emil
Gagnan made it. With unregulated compressed air supplies,
with sea pressure increasing with depth, there was always a
danger of an underwater
swimmer's lung collapsing.
The aqualung has a special valve regulating the air supply.
As the diver breathes out, the pressure of his breath opens
outlet valve which also shuts off the air supply. As he
breathes in, the internal pressure falls and the outside
water pressure closes the outlet valve and switches the
compressed air supply back on. The air flows in
until the pressure in the valve is the same as the pressure
of the outside water. Then it cuts off.