46 C.F.R. § 122.610 Watertight doors and watertight hatches.
Title 46 - Shipping
Watertight doors and watertight hatches must be marked on both sides in clearly legible letters at least 25 millimeters (1 inch) high: “WATERTIGHT DOOR—KEEP CLOSED” or “WATERTIGHT HATCH—KEEP CLOSED”, unless such markings are deemed unnecessary by the cognizant OCMI. [CGD 85–080, 61 FR 935, Jan. 10, 1996, as amended by CGD 97–057, 62 FR 51047, Sept. 30, 1997]
Title 46: Shipping
PART 122—OPERATIONS
Subpart F—Markings Required
§ 122.610 Watertight doors and watertight hatches.