46 CFR §171.124

1. (a)Each hatch exposed to the weather must be watertight; except that, the following hatches may be weathertight:
   1. (1)Each hatch on a watertight trunk that extends at least 12 inches (30.5 centimeters) above the weather deck.
   2. (2)Each hatch in a cabin top.
   3. (3)Each hatch on a vessel that operates only on protected waters.
2. (b)Each hatch cover must—
   1. (1)Have securing devices; and
   2. (2)Be attached to the hatch frame or coaming by hinges, captive chains, or to other devices to prevent its loss.
3. (c)Each hatch that provides access to crew or passenger accommodations must be operable from either side.
4. (d)Except as provided in paragraph (e) of this section, a weathertight door with permanent watertight coamings that comply with the height requirements in table 171.124(d) must be provided for each opening located in a deck house or companionway that—
   1. (1)Gives access into the hull; and
   2. (2)Is located in—
      1. (i)A cockpit;
      2. (ii)A well; or
      3. (iii)An exposed location on a flush deck vessel.
5. (e)If an opening in a location specified in paragraph (d) of this section is provided with a Class 1 watertight door, the height of the watertight coaming need only be sufficient to accommodate the door.