The dry dock is a structured area wherein construction, repairs and maintenance of merchant vessels and boats are carried out. The unique construction allows the water to be filled up in an area, also known as a lock so that vessels can be manoeuvred in and out of the area. Once the vessel enters the dry dock, the gates are closed and the seawater is drained out so that hull and other areas of the ship which have been exposed to seawater for a long time are available for carrying out...
https://www.marineinsight.com/guidelines/dry-dock-types-of-dry-docks-requirements-for-dry-dock/