diving bell

A diving bell is a hollow structure providing a dry environment for underwater workers. Early diving bells were bell-shaped, filled with compressed air, and open at the bottom to give access to the seabed. The bathysphere, which made its first dive in 1930, was spherical, made of steel, and could withstand considerable pressures, but it was restricted to depths within reach of supply and winch cables. It has been replaced by the bathyscaphe.