(a) Unless one or more extensions are authorized by the Commandant (CG-CVC), each OSV must be placed in drydock or hauled out for examination twice each 5 years with no interval between examinations exceeding 3 years.

(b) The owner or operator shall notify the cognizant OCMI whenever the OSV is drydocked for any reason. This OCMI, upon notification, will determine whether to assign a marine inspector to examine the underwater hull of the vessel.

(c) The internal structural members of an OSV must be examined at the same intervals required for drydocking by paragraph (a) of this section.

(d) At each drydocking required by paragraph (a) of this section, for an OSV of 100 or more gross tons, a tailshaft survey must be conducted as required by § 61.20-15 of this chapter.

(e) At each drydocking required by paragraph (a) of this section, for an OSV of less than 100 gross tons, the propeller or tailshaft must be drawn for examination if the cognizant OCMI deems drawing it necessary.

(f) Vessels less than 15 years of age (except wooden hull vessels) that are in salt water service with a twice in 5 year drydock interval may be considered for an underwater survey instead of alternate drydock examinations, provided the vessel is fitted with an effective hull protection system. Vessel owners or operators must apply to the Officer in Charge, Marine Inspection (OCMI), for approval of underwater surveys instead of alternate drydock examinations for each vessel. The application must include the following information:

(1) The procedure to be followed in carrying out the underwater survey;

(2) The location where the underwater survey will be accomplished;

(3) The method to be used to accurately determine the diver location relative to the hull;

(4) The means that will be provided for examining through-hull fittings;

(5) The means that will be provided for taking shaft bearing clearances;

(6) The condition of the vessel, including the anticipated draft of the vessel at the time of the survey;

(7) A description of the hull protection system; and

(8) The name and qualifications of any third party examiner.

(g) Vessels otherwise qualifying under paragraph (f) of this section, that are 15 years of age or older, may be considered for continued participation in or entry into the underwater survey program on a case-by-case basis if—

(1) Before the vessel's next scheduled drydocking, the owner or operator submits a request for participation or continued participation to the cognizant District Commander;

(2) During the vessel's next drydocking, after the request is submitted, no appreciable hull deterioration is indicated as a result of a complete set of hull gaugings; and

(3) The results of the hull gauging and the results of the Coast Guard drydock examination together with the recommendation of the OCMI, are submitted to Commandant (CG-CVC) for final approval.