An in-water or drydock inspection of the hull, rudder, propeller, and sea valves required by classification societies every two to five years.
In practice
The docking survey scope includes examining the condition of the anti-corrosion coating system, any impressed current cathodic protection (ICCP) system or sacrificial anodes, rudder bearing clearances, propeller blade condition and pitch, and sea valve operation. Any areas of wasting below the allowable limits specified in class rules must be rectified by insert plating, doubler plate, or replacement before the vessel is reclassed. In-water surveys are accepted as an alternative to drydocking by most classification societies under defined conditions, including acceptable underwater visibility and a clean hull free of heavy fouling that would conceal structural defects.
Regulatory detail & full definition
A docking survey is a classification society inspection of a vessel's underwater hull, appendages, and sea openings, conducted either in a dry condition (graving dock or floating dock) or by approved in-water survey (IWS) using divers or remotely operated vehicles. Classification rules require that the underwater hull and all related fittings are examined at defined intervals — typically every two and a half years for most vessel types — to assess corrosion, wasting, denting, shell plating condition, and the condition of the rudder, propeller, shaft brackets, bilge keels, and sea valve chests.
The docking survey scope includes examining the condition of the anti-corrosion coating system, any impressed current cathodic protection (ICCP) system or sacrificial anodes, rudder bearing clearances, propeller blade condition and pitch, and sea valve operation. Any areas of wasting below the allowable limits specified in class rules must be rectified by insert plating, doubler plate, or replacement before the vessel is reclassed. In-water surveys are accepted as an alternative to drydocking by most classification societies under defined conditions, including acceptable underwater visibility and a clean hull free of heavy fouling that would conceal structural defects.