46 C.F.R. § 131.510 – Draft and loadline markings.

(a) The master of each vessel on an ocean or coastwise voyage shall enter in the vessel's logbook the drafts of the vessel, forward and aft, when leaving port.
(b) The master of each vessel subject to the requirements of subchapter E of this chapter shall, upon departure from port on an ocean or coastwise voyage, enter in the vessel's logbook a statement of the position of the loadline markings, port and starboard, relative to the surface of the water in which the vessel is then floating.
(c) If the master, when recording drafts, compensates for the density of the water in which the vessel is floating, he or she shall note this density in the vessel's logbook.