The acronym HAWASSI© stands for Hamiltonian Wave-Ship-Structure Interaction. The Hamiltonian formulation calculates phase resolved waves in a dimension-reduced way (Boussinesq with exact or optimized dispersion); the interior fluid motion can be recovered in a post-processing step. The explicit time evolution with automatic time step conserves the approximate energy exactly and avoids instabilities and unwanted dissipation. Wave-Ship-Structure Interaction refers to waves affected by bathymetry, harbour walls, breakwaters, etc. (Wave-ship interactions will become available in later versions).