The difficulty of movement in a liquid world and the problems of constantly increasing and decreasing pressure also had to be solved. Diving with an air supply was only being done by a few highly trained people using complicated, cumbersome deep-sea suits and helmets with high-pressure airlines to the surface.
In 1943 Captain Jacques-Yves Cousteau and Emile Gagnan invented the aqualung. This was the key that unlocked the secrets of the underwater world.
With this equipment divers are no longer tied to an airline leading to the surface or weighed down with heavy equipment. Their air supply is carried with them in high-pressure cylinders strapped to their backs.
Breathing is as automatic and natural as breathing on the surface. A demand regulator attached to the air cylinder automatically adjusts breathing air to exactly the same pressure as that of the surrounding water. There are no valves to adjust. All the diver needs to do is breathe. The aqualung gives him air at exactly the right pressure, no matter what the depth.
After the invention of the aqualung, skin diving spread tremendously all over the world, and a lot of other types of equipment were made to go with it.