46 CFR 137.335: Underwater survey in lieu of drydocking

Last reviewed: October 14, 2026

This section covers the underwater survey in lieu of drydocking (UWILD) for towing vessels. A vessel is eligible if the Coast Guard determines that the listed conditions are met, and the owner or managing operator must apply to the cognizant OCMI at least 90 days before the next required drydock examination. For a vessel 15 years of age or older, the Commandant may approve a UWILD at alternating intervals if paragraph (c) conditions are met.

Applies toAll towing vessels subject to this subchapter.

What it says

  1. A vessel is eligible for UWILD if the Coast Guard determines that the conditions listed in paragraph (a) are met.

    46 CFR 137.335(a)“A vessel is eligible for UWILD if the Coast Guard determines that:”

  2. If a TSMS is applicable to the vessel, the TSMS may include policies and procedures for employing and documenting a UWILD.

    46 CFR 137.335(a)“If a TSMS is applicable to the vessel, the TSMS may include policies and procedures for employing and documenting an underwater survey in lieu of drydocking (UWILD).”

  3. One condition the Coast Guard determines under paragraph (a) is that the vessel is less than 15 years of age. Paragraph (c) gives an exception for older vessels.

    46 CFR 137.335(a)(3)“The vessel is less than 15 years of age;”

  4. Another condition the Coast Guard determines is that the vessel has a steel or aluminum hull.

    46 CFR 137.335(a)(4)“The vessel has a steel or aluminum hull; and”

  5. The owner or managing operator must submit an application to the cognizant OCMI at least 90 days before the vessel's next required drydock examination.

    46 CFR 137.335(b)“The owner or managing operator must submit an application to the cognizant OCMI at least 90 days before the vessel's next required drydock examination.”

  6. The application must include the means for examining all through-hull fittings and appurtenances.

    46 CFR 137.335(b)(4)“The means for examining all through-hull fittings and appurtenances;”

  7. If a vessel is 15 years of age or older, the Commandant may approve a UWILD at alternating intervals, provided the conditions in paragraph (c) are met. The vessel does not need to be less than 15 years of age, but must otherwise comply with paragraphs (a) and (b).

    46 CFR 137.335(c)“If a vessel is 15 years of age or older, the Commandant may approve a UWILD at alternating intervals provided that:”

  8. For an older vessel, a complete set of hull gauging taken during the drydock examination preceding the survey must have indicated that the vessel was free from hull deterioration.

    46 CFR 137.335(c)(2)“a complete set of hull gauging was taken which indicated that the vessel was free from hull deterioration.”

Common questions

How far ahead must I apply for an underwater survey in lieu of drydocking?

The owner or managing operator must apply to the cognizant OCMI at least 90 days before the vessel's next required drydock examination.

“The owner or managing operator must submit an application to the cognizant OCMI at least 90 days before the vessel's next required drydock examination.”

Can a towing vessel 15 years or older use UWILD?

The Commandant may approve a UWILD at alternating intervals for a vessel 15 years of age or older if the conditions in paragraph (c) are met.

“If a vessel is 15 years of age or older, the Commandant may approve a UWILD at alternating intervals provided that:”

What hull types are eligible for UWILD?

One condition the Coast Guard determines is that the vessel has a steel or aluminum hull, among the other listed conditions.

“The vessel has a steel or aluminum hull; and”

The text of 46 CFR 137.335

Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR

Underwater survey in lieu of drydocking

(a) This section applies to all towing vessels subject to this subchapter. If a TSMS is applicable to the vessel, the TSMS may include policies and procedures for employing and documenting an underwater survey in lieu of drydocking (UWILD). A vessel is eligible for UWILD if the Coast Guard determines that:

(1) There is no obvious damage or defect in the hull adversely affecting the seaworthiness or fitness for the vessel's route or service;

(2) The vessel has been operated satisfactorily since the last drydocking;

(3) The vessel is less than 15 years of age;

(4) The vessel has a steel or aluminum hull; and

(5) The vessel is fitted with a hull protection system.

(b) The owner or managing operator must submit an application to the cognizant OCMI at least 90 days before the vessel's next required drydock examination. The application must include:

(1) The procedure for carrying out the underwater survey;

(2) The time and place of the underwater survey;

(3) The method used to accurately determine the diver's or the remotely operated vehicle's location relative to the hull;

(4) The means for examining all through-hull fittings and appurtenances;

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

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

(7) The names and qualifications of all personnel involved in conducting the UWILD.

(c) If a vessel is 15 years of age or older, the Commandant may approve a UWILD at alternating intervals provided that:

(1) All provisions of paragraphs (a) and (b) of this section are complied with, except that the vessel does not need to be less than 15 years of age; and

(2) During the vessel's drydock examination preceding the underwater survey, a complete set of hull gauging was taken which indicated that the vessel was free from hull deterioration.

The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.