Hydrostatics is a principle of marine engineering concerned with the conditions governing a vessel's behavior in water. The properties of hydrostatics include vessel stability, the vessel's ability to restore itself to an upright position when inclined by sea, wind and loading conditions. Hydrostatics involves the computation of buoyancy and displacement; trim, weight and center of gravity, line plans, tank capacity and creation of hull form.
Marine hydrodynamics is concerned with the flow of water around a vessel's hull, bow, stern, propeller blades and thruster tunnels. Hydrodynamics involves resistance in terms of motion in water, caused by the flow of water around the hull of a vessel. It also deals with the effect of waves on resistance, viscosity and surface tension and maneuverability of the vessel for maintaining position and direction.
Propulsion refers to the mechanism that provides a vessel with the ability to move through water. To enable a vessel to move in water, propellers, water jets or thrusters may be used. Most modern vessels are propelled by mechanical systems with an engine to turn the propeller; jet drives have an impeller. The energy to drive the propellers or thrusters is generally provided by internal combustion engines. There are some vessels propelled through energy provided by solar or nuclear energy.
Marine vessels have a wide range of requirements necessary to make them self-sustaining units while at sea. Auxiliary systems include fuel, bilge, ballast, cooling water, compressed air, heating, ventilation, air conditioning, refrigeration, electrical, sanitary and sewage. There are various components that make up auxiliary systems in marine engineering including compressors, valves, pumps, piping, purifiers, deck machinery, steering machinery, heat exchangers, sewage and refrigeration plants and distilling plants.