Underwater in-lieu of dry dock (UWILD) inspections are required by the classifications society (aka class) to be carried out periodically. These inspections require the technical superintendent and the class surveyor who will inspect the videos that will be fed by the underwater divers. UWILD inspections require live feed video rather than still images. Rudder pintle readings (or measurements) and tail shaft reading are also part of the UWILD inspection.
Non UNWILD inspection is carried out on an ad-hoc request such as when a vessel runs aground or a particular type of cleaning is required. In such a case the captain and crew will need to know the status of the vessel's hull and an underwater inspection is carried out with the class surveyor.
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