The Commercial Logic
Drydocking removes a vessel from service. An in-water survey does not, which is why owners ask for it whenever the survey purpose allows.
Whether class accepts an in-water survey in place of a docking survey depends on the society, the vessel, its age and the survey type. That confirmation belongs with the society, not with the diving contractor.
What Can Be Established Afloat
A well-executed in-water survey covers a substantial part of the hull scope.
- Hull plating condition and coating breakdown
- Propeller, rudder and stern gear condition
- Sea inlets, gratings and openings
- Anode condition and wastage
Where Drydock Remains Necessary
Structural work, full coating renewal and anything requiring dry access or internal opening still needs a dock. The in-water survey then serves a different purpose: deciding when that dock is needed and what to prepare for it.