The large cruise ship is a type of ship with large size and high added value, which has been increasingly studied and developed during the recent years. Since a large cruise ship often sails in the crowded waters such as harbor and coastal area, the study of the hydrodynamic interaction between the cruise ship and other ships is crucial to ensure the navigation safety. Taking a large cruise ship and a KCS container ship as the study object, the hydrodynamic characteristics of the two ships at different longitudinal positions, transverse positions, and ship speeds in both deep and shallow water are predicted in model scale by solving the unsteady Reynolds-averaged Navier-Stokes (RANS) equations, and the variations of the hydrodynamic interactions between the two ships are identified. It is shown that different relative positions and ship speeds have significant effects on the lateral force and yaw moment acting on the two ships. The hydrodynamic interaction between the two ships in shallow water is more remarkable, and the relatively smaller ship is more affected by the ship-to-ship interaction.