drydock

A drydock is a facility that allows ships and other watercraft to be constructed, maintained, or repaired in a dry environment by removing water from a watertight basin.

There are two main types: fixed graving docks, which are permanently built basins with gates at each end that are sealed and pumped dry, and floating drydocks, which are buoyant structures that can be submerged to admit a vessel and then pumped dry to create a stable working space. Graving docks rely on a solid, masonry or concrete chamber, while floating drydocks consist of a hollow hull or pontoon with ballast systems.

A vessel enters the dock, the gates are closed, and water is pumped out to create a dry working area. The hull is then supported by blocks and keel supports, and divers may access submerged areas for inspection, cleaning, or repair. Once work is complete, water is reintroduced and the vessel exits the dock.

Drydocks are used for hull cleaning and painting, inspection for corrosion and damage, repair of hull plating or propulsion systems, replacement of bearings or shafts, and other maintenance tasks. They are also employed in ship construction and for maintenance of offshore structures.

Historically, drydocks advanced from simple docks to sophisticated concrete and steel basins capable of handling large vessels. Today, they remain essential in commercial shipyards and naval facilities, enabling scheduled maintenance, major repairs, and life-extension work under controlled conditions with environmental and safety standards guiding operation.