The peculiarities of underwater sound conduction through the body of the Black Sea bottlenose dolphin (Tursiops truncatus p.) were investigated to elucidate the mechanisms of acoustic orientation of marine mammals. By using the method of instrumental conditioned reflexes with food reinforcement, underwater hearing thresholds in the bottlenose dolphin depending on signal parameters (tonal pulses and various noises) and sound conduction pathways were measured under conditions of full and partial (with the head out of water and sound being conducted through the body tissues) submergence of the animal into water. The underwater hearing thresholds increased by 6-27 dB upon sound conduction through the body tissues (to the least extent for tonal pulses of 10 and 20 kHz). The hearing thresholds for tonal pulses and narrow-band noises were very similar both under conditions of full and partial submergence of the animal into water.