The aim of the presentation is to demonstrate the possibilities of predicting loads on partially submerged, moving structures, in particular on tanks in ships and on offshore platforms. Since tanks can in reality move arbitrarily, we are using the moving grid approach and a Finite Volume solution method designed to cater for arbitrary motions of polyhedral control volumes. The motion of liquid is computed using an interface-capturing scheme which allows overturning and breaking of waves. By performing a coupled simulation of the flow and vessel motion, it is possible to obtain a realistic response of the liquid in a tank to external excitation, e.g. by sea waves. Results are first presented for several tanks whose motion is prescribed in accordance with experimental setups, with which the solutions are compared. A very good agreement between pressures computed in simulations and experimental data at representative locations is obtained. It was possible by means of simulation to clearly distinguish between offresonance and resonance cases, in which peak pressures reached the highest values, in accordance with experimental observations. Following validation by experimental data in laboratory setups, we demonstrate the plausibility of simulation of both vessel motion and the flow inside and outside vessel. The forces and moments exerted by the sea cause the vessel to move, which excites the sloshing of liquid in tanks. For the computation of vessel motion, both sea-induced forces and forces due to sloshing in tanks are taken into account when determining the resultant forces and moments. While there are no experimental data to compare with, the results look plausible and encourage further validation and application studies.