46 CFR §179.360

1. (a)A hatch exposed to the weather must be watertight, except that the following hatches may be weathertight:
   1. (1)A hatch on a watertight trunk that extends at least 305 millimeters (12 inches) above the weather deck;
   2. (2)A hatch in a cabin top; and
   3. (3)A hatch on a vessel that operates only on protected waters.
2. (b)A hatch cover must:
   1. (1)Have securing devices; and
   2. (2)Be attached to the hatch frame or coaming by hinges, captive chains, or other devices of substantial strength to prevent its loss.
3. (c)A hatch cover that provides access to accommodation spaces must be operable from either side.
4. (d)A weathertight door must be provided for each opening located in a deck house or companionway. Permanent watertight coamings must be provided as follows:
   1. (1)On a vessel on an exposed or partially protected route, a watertight coaming with a height of at least 150 millimeters (6 inches) must be provided under each weathertight door in a cockpit or a well, or on the main deck of a flush deck vessel.
   2. (2)On a vessel on a protected route, a watertight coaming with a height of at least 75 millimeters (3 inches) must be provided under each weathertight door in a cockpit or a well.
   3. (3)The height of the watertight coaming for a hinged watertight door need only be sufficient to accommodate the door.