The audibility threshold performance of the human ear submerged in water at ear depths of 12 and 35 ft was compared to its performance in air. Threshold SPL's at 125, 250, 500, 1000, 2000, 4000, and 8000 Hz from five male and three female divers wearing open‐circuit SCUBA equipment were obtained by the Békésy technique. Differences between water and air conduction thresholds ranged from 18 dB SPLre0.0002 μbar at 125 Hz to 56 dB at 8000 Hz. Underwater thresholds ranged between 58 and 74 dB SPL, with maximum sensitivity around 500 Hz. Maximum sensitivity for air conduction thresholds was obtained at 2000 Hz. Slightly higher thresholds were obtained at the 35‐ft ear depth than at the 12‐ft depth. Tentatively, the data suggest the importance of bone‐conduction mechanisms in underwater hearing. However, it is apparent that further research must be carried out before it will be possible to predict the character and mechanism of the human ear submerged in water.