This paper describes an ultrasonic sensor for integration on a UUV. The sensor is characterised by a wide-angle spatial transmission pattern, high range resolution, short minimum detection range and fast response time. For UUV operation in proximity to marine platforms, the seafloor or other hazards, sensors which have ranges below 2m with minimum detection ranges to a few centimetres are needed. Commercial sensors that adequately fulfil this role are as yet not available. The sensor presented has been designed to provide sensor coverage at these close ranges. It can be used to augment data obtained using conventional sonar and vision sensors in target applications such as station keeping, docking and close quarter's collision avoidance.