Zebrafish use gas-filled swimbladders to maintain nearly neutral buoyancy and three-dimensional orientation (pitch and roll). The two-chambered swimbladder also contributes to hearing of the fish, via the Weberian apparatus which connects the anterior chamber to the acoustic labyrinth. Swimbladder volume, and thus its contributions to all these functions, varies with depth-related pressure as described by Boyle’s Law. The swimbladder volume at a given depth also depends on the elasticity of the swimbladder wall. In this study the effects of pressure on swimbladder volume, both in vivo and in situ, and the behaviour of the whole animal were observed, using pressure tanks which allowed simulations of vertical movement within the water column to a depth of 300 cm and a return to surface from a depth of 300 cm; results showing the anterior chamber to be highly compliant in contrast to a minimally compliant posterior chamber. Future work will focus on the active control of the swimbladder through autonomic nervous system control of this organ. Ongoing experiments on zebrafish hearing have shown repeatable increases in swimming activity (arousal) in adult zebrafish during exposure to noise stimuli. Comparison of the results of these tests to zebrafish tested after simulated depth changes will elucidate any effects that changes in swimbladder volume may have on auditory function of these fish.