The Maritime Research Institute Netherlands (MARIN) supplies innovative products for the offshore industry and shipping companies. Among their products are highly realistic real-time bridge simulators. Currently, the waves are deterministic and are not affected by ships, moles, breakwaters, piers, or any other object. To bring the simulators to the next level, a new interactive wave model is being developed. This is the so-called Variational Boussinesq model (VBM) as proposed by Klopman. The main improvement will be that the waves and ships really interact, i.e., the movements of the ship are influenced by the waves and the waves in their turn are influenced by the ship. However, one pays for the higher realism: the new model is much more computational intensive and therefore a really fast solver is needed to fulill the requirements of real-time simulation. In this thesis we present how a very efficient iterative solver can be combined with a very efficient implementation on the graphical processing unit (GPU). Speed up factors of more than 30 can be obtained for realistic problems. With the new solver interactive waves can be computed in real-time for large domains. Necessary theory on iterative solvers and GPU programming is included.