Powering, maneuvering, and seakeeping constitute the three central areas of ship hydrodynamics. Although this article focuses on these areas in connection with displacement ships, that is, vessels supported entirely (or almost entirely) by hydrostatic forces, basic concepts of powering, maneuvering, and seakeeping are also critical to an understanding of high-speed craft, such as planing boats, hydrofoil craft, and air-cushion vehicles, even if the physical phenomena governing dynamically supported craft are somewhat different.