The contra-rotating marine current turbine concept developed by the Energy Systems Research Unit at the University of Strathclyde is aimed at extracting energy in a wide range of water depths by 'flying' a neutrally-buoyant device from a flexible, tensioned mooring. After successful proof of concept turbine trials, the development programme has moved on to investigate the performance of a scaled prototype of the complete system incorporating the turbine, submersible contra-rotating generator and mooring. The turbine/generator assembly has been tested in a towing tank, and the entire system is now undergoing sea trials. An investigation into turbine wake development (an area in which it is hoped that the contra-rotating turbine will have uniquely beneficial properties) has recently begun. Small single-rotor model turbines have been deployed in a flume. Trends observed so far are in accordance with those observed by other researchers