Underwater communication is necessary for scientific applications like monitoring climate change, algae bloom, seismic activities, industrial applications like oil exploration and military applications. The deployment of underwater sensor nodes is being carried out after the successful implementation of terrestrial sensor networks. With the disadvantages faced by traditional communication methods when deployed underwater, the underwater sensor networks are fast gaining acceptance. The problems faced by underwater nodes are different from those faced by terrestrial nodes. In this paper we provide a study of the developments in underwater wireless sensor networks. The use of Underwater Wireless Sensor Networks (UWSN) with Autonomous Underwater Vehicles (AUN) has helped in monitoring the ocean beds, oil exploration, military observations etc.