46 CFR §140.610

1. (a)All towing vessels must be operated in a manner that minimizes the risk of down-flooding and progressive flooding.
2. (b)The master must ensure that all hatches, doors, and other openings designed to be watertight or weather-tight function properly.
3. (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:
   1. (1)When access is needed through the opening for transit;
   2. (2)When operating on rivers with a tow, if the master determines the safety of the vessel is not compromised; or
   3. (3)When operating on lakes, bays, and sounds, without a tow during calm weather, and only if the master determines that the safety of the vessel is not compromised.
4. (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
5. (e)When downstreaming, all exterior openings at the main deck level must be closed.
6. (f)Decks and bulkheads designed to be watertight or weathertight must be maintained in that condition.