History
   
A knowledge of the contributions of deep sea divers in years gone by is necessary for us to truly appreciate our ability to take to the blues in the new millennium. Our debt to our predecessors can only be paid if we continue their quest for knowledge and diving experience.

The earliest reference to underwater diving techniques occurs in the manuscripts of the Greek philosopher Aristotle, which refer to a diving bell used by forces of Alexander the Great to clear the harbor at Tyre in 332 BC. This contraption, shaped like a bell, was actually a large wooden barrel that a diver could place over the head and upper body while walking on the bottom of the sea. Underwater, the pressure of the air trapped inside the barrel displaced any water that might enter. This displacement created an airspace where the diver could breathe and see. 

In 1716, English astronomer Edmond Halley invented a bell that allowed divers to stay at about 60 ft (18 m) for an hour and a half. His bell consisted of a wooden shell with windows to admit light from the surface. Air was supplied to divers through leather tubes connected to air casks that could be lowered into the water as needed. As the casks were lowered below the bell, increasing water pressure forced air up through the tubes into the upper part of the diving bell where the divers could inhale it.

These early inventions led to the development of more sophisticated diving bells that are used today. Modern diving bells are constructed of materials such as steel that can withstand extreme water pressure at lower depths. They also have communication systems that link them to the surface, and lighting and heating systems that provide divers with a comfortable working environment. These bells are a means of working on the underwater portions of bridges, piers, and jetties. Diving bells are also used to transport commercial divers to their underwater workstations.

Equipment now used for scuba diving began to appear in the 1800s. In 1819 German inventor August Siebe developed the first diving suit-a copper helmet attached to a canvas and leather suit. Hoses supplied air to the diver by a surface pump. The hoses were attached to the helmet, and the pressure the air provided kept the water level below the diver's chin. Weights worn around the chest kept the diver from rising to the surface when more air was supplied to the helmet. Siebe's suit freed divers to explore the bottom of the sea on foot, and windows in the helmet increased what divers could see. Whereas a bell only permitted divers to see what was below the bell's opening, Siebe's suit allowed them to see in all directions, including the surface above.

The two pioneers who receive most credit for inventing the modern scuba system are Frenchmen Jacques Cousteau and Emil Gagnon. Their invention, called the Aqua-Lung, was first successfully used in 1943. It allowed divers to breathe underwater without a cumbersome diving suit. The Aqua-Lung consisted of a valve-operated hose connecting the diver's mouth to a high-pressure cylinder worn on the back. For the first time, anyone in reasonable physical condition could don the equipment and explore the underwater environment. And for the first time, people could dive for recreation, not just as a means of accomplishing work.

Innovators are also developing mini-submersibles that will enable scientists and researchers to explore the bottom of the ocean at a fraction of previous costs. Most of these units are small, highly maneuverable, and extremely safe. They have windows for viewing and mechanical arms for working and gathering scientific samples.

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