You are OOW. Fog closes in suddenly and visibility drops to 400m. You cannot immediately raise the master by intercom. Can you reduce speed without a master's order?

A. OOW AUTHORITY TO ACT WITHOUT MASTER IN EMERGENCY — YES: STCW Convention Regulation VIII/2 and COLREG Rule 19/Rule 6 collectively impose on the OOW a duty of safe navigation which cannot be suspended because the master is temporarily unavailable. SPECIFIC AUTHORITY: (1) COLREG Rule 6 requires any vessel to proceed at safe speed having regard to prevailing conditions. If visibility has dropped and you are exceeding safe speed, you have both the authority AND the duty to reduce speed — immediately; (2) STCW Code A-VIII/2 Para 51: the OOW is responsible for the safety of the vessel and must immediately take action if the vessel's safety is endangered, including making all necessary manoeuvres; (3) COMPANY SMS: most company SMS documents include a clause stating that the OOW has authority to take immediate action for the safety of the vessel without awaiting master's order; (4) PROCEDURE: REDUCE SPEED to safe speed immediately. Sound fog signal. Continue trying to reach master. LOG the action — time, reason for speed reduction, speed reduced to. BRIEF master fully when he/she arrives; (5) NEVER delay safety action because you cannot first speak to the master. The duty to maintain safe speed is absolute. The master, when informed, should support your decision — if he/she does not, this itself becomes a safety concern to escalate.

B. The OOW does not have authority to alter speed without the master's order unless the vessel is in immediate collision danger. Fog alone does not constitute an immediate danger justifying speed change.

C. The OOW should maintain current speed until the master is reached. If a collision then occurs, the OOW is protected because he/she followed proper chain-of-command procedure by waiting for master authorisation.

D. Only the master or pilot can reduce speed. The OOW should post additional lookouts and sound fog signals while waiting for the master's instruction.

A. SAFE SPEED IN RESTRICTED VISIBILITY — Rule 6 assessment (COLREG Rule 6): safe speed requires consideration of: (a) state of visibility (300m — severely restricted); (b) traffic density (Dover Strait is one of the world's busiest waterways — separation scheme traffic plus local traffic); (c) manoeuvring ability — your vessel's stopping distance at 12 knots (a 140m bulk carrier may take 15+ ship lengths to stop); (d) background lighting at night; (e) draught — your squat in shallow Dover Strait approaches. AT 12 KNOTS WITH 300M VISIBILITY: stopping distance will greatly exceed 300m — you cannot stop within the distance you can see. Rule 8(e) requires reduction to minimum steerage way if necessary to avoid collision. IMMEDIATE ACTIONS: (1) Sound fog signal — one prolonged blast every 2 minutes (Rule 35a — power-driven vessel underway making way); (2) Reduce speed to safe speed — likely 5-6 knots or less to ensure vessel CAN STOP within visibility range; (3) Post extra lookout — Rule 5 — additional lookouts on bow in fog; (4) ARPA on — operating on appropriate scale, all targets tracked; (5) VHF Ch 16 / Ch 11 (Dover VTS DOVER COASTGUARD) monitored; (6) Navigation lights on; (7) Master already called — correct. Safe speed is your judgement call — document your reasoning in the log.

B. Safe speed in fog is defined as half the vessel's normal service speed. At 12 knots service speed, 6 knots is automatically the correct safe speed under COLREG Rule 6.

C. Rule 6 safe speed assessment applies only when vessels have radar — a vessel without radar is exempt from safe speed requirements in restricted visibility.

D. With visibility of 300m, the vessel should anchor immediately in the Dover Strait to await improvement, regardless of traffic density or depth.

A. RULE 19(d) — Action when radar contact detected (no visual contact): COLREG Rule 19(d): a vessel which detects by radar only another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists. If so, take avoiding action in ample time. The action must be: (a) A LARGE ALTERATION OF COURSE — Rule 19(d)(i): if possible, avoid an alteration of course to port for a vessel forward of the beam other than for a vessel being overtaken; (b) AVOID ALTERING COURSE TOWARDS A VESSEL ABEAM OR ABAFT THE BEAM — Rule 19(d)(ii); (c) REDUCE SPEED — reducing speed, stopping engines, or reversing may be needed. IN YOUR SCENARIO: CPA 0.1nm is a close-quarters situation. TCPA 8 minutes gives time for action. RECOMMENDED ACTION: (1) Reduce speed immediately (further — to minimum steerage); (2) Alter course to starboard — large alteration (minimum 30-40°) to open the CPA; (3) Sound appropriate fog signals; (4) Monitor ARPA to confirm action is working — CPA must open; (5) DO NOT alter to port (risk of swinging your bow into the other vessel's path); (6) VHF — if other vessel is a known contact, alert them, but do not rely on VHF agreement. Rule 19 is clear — radar action must be early, substantial, and effective.

B. With CPA 0.1nm and TCPA 8 minutes, the situation is not yet a close-quarters situation under COLREG Rules. Maintain course and speed while monitoring the target.

C. Call the other vessel on VHF Ch 16 and agree a port-to-port passing. Once verbal agreement is reached, no course alteration is necessary.

D. Stop engines and anchor immediately — Rule 19 requires vessels to anchor when a close-quarters situation develops in restricted visibility.