Code of Federal Regulations Title 46. Shipping § 46.140.610 Hatches and other openings

(a) All towing vessels must be operated in a manner that minimizes the risk of down-flooding and progressive flooding.

(b) The master must ensure that all hatches, doors, and other openings designed to be watertight or weather-tight function properly.

(c) The master or officer in charge of a navigational watch must ensure all hatches and openings of the hull and deck are kept tightly closed except:

(d) Where installed, all watertight doors in watertight bulkheads must be closed during the operation of the vessel, unless they are being used for transit between compartments;  and

(e) When downstreaming, all exterior openings at the main deck level must be closed.

(f) Decks and bulkheads designed to be watertight or weathertight must be maintained in that condition.