The maneuvering characteristics are highly affected by the under‐keel clearance. In shallow water, the results of standard maneuvers reveal a decreased maneuverability and an increased straight‐line stability. This modified behavior is mainly to be ascribed to the modified flow around the hull, but also the control forces exerted by rudder and propeller are different compared to the deep‐water case. Besides the effect of vertical limitations, a ship navigating parallel to the horizontal boundaries of navigation areas will also experience the so‐called bank effects, that is, disturbing forces and moments due to the asymmetry of the flow around the hull.
In some harbors and their approach channels, the bottom is covered with a layer of fluid mud. This not only complicates bottom survey, but also affects a ship's propulsive performance and maneuvering due to the specific rheological properties of the mud layer and to the generation of internal waves in the interface between water and mud. Finally, different types of hydrodynamic interaction between ships may take place in restricted waters, due to encountering and overtaking maneuvers, the effect of passing ships on moored vessels, lightering operations, and ship–tug interactions.