Watchkeeping & rest hours

STCW Code Section A-VIII/1 and the Maritime Labour Convention 2006 (MLC, Standard A2.3) together define how long a seafarer can work, how much rest must be given, and how the bridge and engine watches are organised. Both conventions apply to all seafarers — flag states must implement whichever provides the more favourable protection.

Standard 4-on / 8-off bridge watches

The traditional foreign-going merchant ship organises three watchkeeping officers and three rating lookouts in a 4-hour-on, 8-hour-off rotation, repeated through every 24 hours:

Watch	Time (LT)	Officer	Old name
Middle	00:00–04:00	Second Officer	Graveyard
Morning	04:00–08:00	Chief Officer	Mate's watch
Forenoon	08:00–12:00	Third Officer	Forenoon
Afternoon	12:00–16:00	Second Officer	Afternoon
Evening	16:00–20:00	Chief Officer	First dog (16-18) / Last dog (18-20)
First	20:00–24:00	Third Officer	First watch

On naval vessels the 16:00–20:00 watch is split into two 2-hour "dog watches" so the rotation is uneven over a 7-day cycle and each crew has a different watch each day. On most merchant ships the dog watches have been merged.

6-on / 6-off and 2-watch systems

Coastal and short-sea ships often operate with only two watchkeepers — typically the Master and the Chief Officer — on a 6-on / 6-off cycle. This system is permitted under STCW so long as the rest-hour minima are met, but is recognised as a fatigue risk and many flag states require additional safeguards.

STCW rest hours (the 10/77 rule)

Daily minimum — at least 10 hours of rest in any 24-hour period.
Weekly minimum — at least 77 hours of rest in any 7-day period.
Daily division — the 10 hours may be divided into no more than two periods, one of which must be at least 6 hours. Intervals between consecutive periods of rest shall not exceed 14 hours.

MLC hours of work alternative

MLC 2006 Standard A2.3 permits flag states to set either a maximum hours of work or a minimum hours of rest:

· Maximum hours of work: 14 hours in any 24-hour period and 72 hours in any 7-day period.
· Minimum hours of rest: as STCW (10/77).

Most flag states adopt the rest-hour version, which aligns with STCW. Records of daily hours must be kept on a standard format, signed by the seafarer and the master, and made available for inspection by port state and flag state authorities.

Permitted exceptions

The 10/77 minima may be exceeded by collective agreement, but only down to no fewer than 70 hours of rest per week, and not for more than two consecutive weeks. Two further exceptions apply at all times: drills (musters, fire and abandon-ship drills) and overriding operational conditions (a casualty or imminent danger to vessel, persons, or environment, or rendering assistance to others in distress).

UMS — unattended machinery spaces

On a UMS-classed ship the engine room is normally unmanned during navigation. The duty engineer is on call from accommodation, with the bridge monitoring engine alarms and a 30-second "dead-man" alarm from the engine control room when an engineer is on rounds. Class notations require a dual independent alarm to a public address, the duty engineer's cabin, and a second engineer's cabin if the first is unanswered within a set interval (typically 3 minutes).

Fatigue management

· The IMO Guidelines on fatigue mitigation and management (MSC.1/Circ.1598, 2019) is the principal soft-law instrument.
· OCIMF, INTERTANKO, and BIMCO publish industry guidance on fatigue and watchkeeping.
· Fatigue is contributory to a large fraction of maritime casualties; SIRE 2.0 and TMSA inspections explicitly probe rest-hour records and night-time work patterns.
· Symptoms to look for in self and shipmates: micro-sleeps, errors of omission, mood change, slow reaction, poor situational awareness on the bridge.

Records

Each seafarer's daily record of work or rest hours is signed by the seafarer and the Master (or a delegate). Records are kept onboard for at least 12 months and are inspected by class during ISM audits and by port state during inspections. A copy is provided to the seafarer on request.