46 C.F.R. § 15.1111 – Work hours and rest periods.

(a) Every person assigned duty as Officer in Charge of a Navigational or Engineering Watch, or duty as Ratings Forming Part of a Navigational or Engineering Watch, or designated safety, prevention of pollution, and security duties onboard any vessel that operates beyond the boundary line, as described in part 7 of this chapter, must receive—
1. (1) A minimum of 10 hours of rest in any 24-hour period; and
2. (2) 77 hours of rest in any 7-day period.
(b) The hours of rest required under paragraph (a) of this section may be divided into no more than two periods in any 24-hour period, one of which must be at least 6 hours in length, and the interval between consecutive periods of rest must not exceed 14 hours.
(c) The requirements of paragraphs (a) and (b) of this section need not be maintained in the case of an emergency or drill or in other overriding operational conditions.
(d) The minimum period of rest required under paragraph (a) of this section may not be devoted to watchkeeping or other duties.
(e) Watchkeeping personnel remain subject to the work-hour limits in 46 U.S.C. 8104 and to the conditions under which crewmembers may be required to work.
(f) The Master must post watch schedules where they are easily accessible. They must cover each affected person under paragraph (a) of this section, and must take into account the rest requirements of this section as well as port rotations and changes in the vessel's itinerary.
(g) Records of daily hours of rest must be maintained onboard the vessel. Each affected person under paragraph (a) of this section must receive a copy of the records pertaining to them, which will be endorsed by the Master or by a person authorized by the Master and by the seafarer.
(h) For every seafarer on call, such as when a machinery space is unattended, the seafarer must have an adequate compensatory rest period if the normal period of rest is disturbed by call-outs to work.
(i) The Master of the vessel may suspend the schedule of hours of rest and require a seafarer to perform any hours of work necessary for the immediate safety of the ship, persons onboard, or cargo, or for the purpose of giving assistance to other ships or persons in distress at sea. As soon as practicable after the situation has been restored, the Master must ensure that any seafarer who has performed work in a scheduled rest period is provided with an adequate period of rest.
(j) In exceptional circumstances, the Master may authorize exceptions from the hours of rest required under paragraphs (a) and (b) of this section provided that:
1. (1) The hours of rest provided for in paragraph (a)(1) of this section may be divided into no more than three periods, one of which must be at least 6 hours in length, and neither of the other two periods are permitted to be less than one hour in length.
  1. (i) Exceptions to paragraph (a)(1) of this section must not extend beyond two 24-hour periods in any 7-day period; and,
  2. (ii) The intervals between consecutive periods of rest must not exceed 14 hours.
2. (2) Exceptions to paragraphs (a)(2) and (b) of this section must not be less than 70 hours of rest in any 7-day period.
3. (3) Exceptions to paragraph (a)(2) of this section are not allowed for more than two consecutive weeks, and the intervals between two periods of exceptions to paragraph (a)(2) must not be less than twice the duration of the longer exception.