Abstract: Underwater sensor networks (UWSNs) can be applied to sea resources reconnaissance, pollution monitoring, assistant navigation, etc., and they have become a hot field in wireless sensor networks. In open and complicated underwater environments, the monitored target is dynamic and uncertain. It is a key topic for sensors to adjust their positions according to the environment and targets, so as to cover the targets in an optimal manner. This paper defines the underwater sensor deployment problem and its performance evaluation metrics, and then presents a fish swarm inspired sensor deployment algorithm. Simulating the behavior of fish swarm and taking the crowd factor into account, the method can drive the sensors to cover almost all the events, and make the sensors density match the events density. Through extensive comparative simulations, we demonstrate that the proposed algorithm can solve the underwater sensor deployment problem effectively and it is be simple, fast in convergence, and realizable in distributed manner.