S201 is an 8.9 tonne vehicle intended for 48hr operation at depths up to 305m. This project is an example of our rapid prototyping capabilities. From outline specification to launch took just 14 months. Dived performance is maximised by attention to streamlining of the outer hull and by the use of advanced motor technology to directly drive the main propeller. Surface running is possible with one crewmember on deck and hatch closed, at speeds up to 6kn in modest sea states, but the vessel's primary mode of deployment is by crane-in.