During the measurement of noise generated inside a standard hard hat and the underwater noise level produced by a pneumatic rock drill and two different high-pressure water jet lances commonly used in underwater work, noise levels were recorded of up to 170.5 dB(A), in relation to a pressure of 1 muPa, in the water close to the diver`s heads. Fortunately, the noise is attenuated by the hoods/helmets worn by the divers and the raised hearing threshold in water and compressed gas. The recorded temporary threshold shifts indicate, however, that lengthy exposure might be hazardous to divers` hearing. This possibility is confirmed by a comparison of the noise levels observed in the present study with hearing damage risk criteria.