Diving helmets are worn by divers who need to speak and hear underwater. A normal diving mask and diving regulator prevent the diver from effectively communicating. Diving helments are mostly used with surface supplied diving: the helmet acts as a firm anchor point on the diver for the umbilical supplying the breathing gas. Divers do heavy or dangerous work underwater also benefit from the head protection provided by the helmet.
Modern helmetdiving suits usually consist of a waterproof one-piece suit made of canvas and rubber that entirely covers the wearer except for the head and hands.
Helmetdiving has the disadvantage of restricting the divers lateral movement because of the connection to the surface.
The limitations imposed on the helmet divers lateral movement (because of the connection to the surface) led to early interest in alternative equipment that would permit freer movement, but the scuba apparatus was not developed by Jacques Yves Cousteau and Emil Gagnan until well into the 20th cent.
Divinghelmets are worn by mainly by professional divers engaged in surface supplied diving.
The helmet seals the whole of the diver's face from the water, allows the diver to see, provides the diver with breathing gas, provides an anchor point on the diver for the umbilical supplying the breathing gas, protects the diver's head when doing heavy or dangerous work and provides voice communications with the surface.
The helmet is more secure than breathing from a mouthpiece, which must be gripped between the teeth, in the event that the diver becomes unconscious.