46 CFR §107.261

1. (a)Except as provided in paragraphs (b), (c), and (d), each unit must be drydocked in the presence of a Coast Guard inspector at least once during each 24 month period after it is issued a Certificate of Inspection.
2. (b)If a unit is column-stabilized, it may be specially examined in lieu of drydocking in accordance with § 107.265 in the presence of a Coast Guard inspector.
3. (c)If a unit is self-elevating, it may be specially examined in lieu of drydocking in accordance with § 107.267 in the presence of a Coast Guard inspector.
4. (d)If a unit is a surface type, it may be specially examined in lieu of drydocking in accordance with § 107.265 in the presence of a Coast Guard inspector if the examination is specifically approved by the Commandant.
5. (e)The master, person in charge, owner, or agent of a certificated unit must notify the appropriate Officer in Charge, Marine Inspection before the unit is drydocked, or specially examined.
6. (f)The master, person in charge, owner, or agent of a certificated unit operating in international service must notify the appropriate Officer in Charge, Marine Inspection at least 60 days before the unit is drydocked or specially examined under § 107.265 or § 107.267.