The TNO underwater warfare (UWW) research programme results in a large number of models used in operational research projects. To enhance the accessibility and re-use of these models for new projects, TNO-FEL has developed the modelling environment ‘MOSES - Maritime Operations Simulation and Evaluation System’. This research environment is based on object oriented simulation techniques, and provides the user with a framework to model, simulate and analyse UWW related problems – as a true underwater warfare testbed. MOSES consists of a computer infrastructure, a repository of models and documentation and tools.These tools support model and system developers as well as operational analysts. ‘Linking’ of models is possible on multiple levels, increasing its integrating capability. The range of MOSES applications is steadily growing: from conceptual models up to operational, sea going systems, from reconstruction of operation up to the use of detailed physics in underwater propagation. The warfare areas cover mine warfare (hunting, as well as sweeping) and anti submarine warfare. Foreseen are topics on torpedo defence and the deployment of unmanned underwater vehicles.