Operations of search and rescue are technically very complicated and cause a potential risk for the rescue team. Therefore a new, autonomously acting rescue system is now being under development. Two mathematical models are presented to compute the hydrodynamics of small twin-hull water craft during a search and rescue process at different sea states. Using three and six degrees of freedom they are capable of simulating the navigation of the controlled rescue boat from the parent ship to the person overboard. 3DOF model is validated by comparison with SIMMAN workshop data and results obtained from 6DOF model. Also a study is performed to evaluate the influence of boat parameters on the manoeuvrability.