Docking Survey
A Docking Survey is the examination of the parts of a ship that are normally underwater — the shell plating, keel, rudder, propeller, sea chests, sea valves and anodes. It is carried out with the ship in dry dock, so class requires it as part of the two dockings normally needed within each five-year period.
The docking survey overlaps the dry-docking work itself: the hull is cleaned and gauged, the rudder and stern-tube clearances are measured, sea valves are opened up, and any steel or coating defects are made good under class supervision. Some ships qualify for an approved in-water survey in lieu of one docking.
The underwater hull is the part a ship cannot inspect at sea, yet it carries the highest corrosion and damage risk. The docking survey — done while the ship is already in dock for maintenance — is how class confirms the below-waterline structure and fittings are sound before the ship trades on for another cycle.
How does a docking survey relate to dry-docking?
They happen together: the ship is in dry dock for hull maintenance, and the class surveyor uses that access to carry out the docking survey of the underwater hull and fittings.