You observe a large vessel on your radar that is travelling at approximately 40 knots on a bearing that would cross your bow. Visually you see a low profile vessel creating a large wake. AIS shows no target. What might this be and what rules apply?

A. At 40 knots with no AIS and low profile: likely a HIGH-SPEED CRAFT (HSC) — possibly a naval vessel, fast ferry, or hovercraft. COLREGs application: (1) Hovercraft (non-displacement, cushion-borne): Rule 23(b) note — a WIG craft shall, in addition to the lights prescribed in paragraph (a), exhibit a high-intensity all-round flashing red light when taking off, landing, and in flight near the surface; (2) Standard HSC (fast ferries, catamarans): subject to full COLREGs; (3) AIS: military vessels are exempt from AIS under SOLAS — a naval fast patrol boat would not show AIS; also some HSC operators do not comply with AIS requirements. At 40 knots, the vessel covers ground very rapidly — a contact at 4nm closing at combined 45 knots has less than 6 minutes to CPA. Action: do NOT use TCPA and CPA at normal planning timescales — act immediately; sound the danger signal (5 short blasts Rule 34(d)); reduce speed; alter to starboard if safe to do so; call on VHF Ch 16.

B. Any vessel over 40 knots is a military vessel exempt from COLREGs. Do not alter course — maintain course and speed to allow the military vessel to plan its manoeuvre.

C. A vessel with no AIS is non-compliant and you have no COLREGs obligation towards it. Navigate on the assumption that it will follow standard COLREGs rules and proceed.

D. At 40 knots the vessel is likely a hydrofoil — these are always give-way vessels under the IMO High Speed Craft Code regardless of geometry.

A. COLREGs Rule 6 (Safe Speed) and ISM Regulation 5 (Master's Overriding Authority) together create an absolute obligation: the Master must navigate at safe speed regardless of commercial pressure. A speed that allows the vessel to stop within half the visibility distance or less is the practical test in restricted visibility. At 0.5nm visibility with significant traffic risk, 6 knots or less is likely necessary. ISM Code Reg 5: "The Company shall establish in the SMS that the Master has the overriding authority and the responsibility to make decisions with respect to safety and pollution prevention and to request the Company's assistance as may be necessary." The charterer's laytime claim cannot override the Master's safety obligation. Action: reduce to safe speed; document the decision in the OLB with the meteorological conditions and COLREGs reasoning; inform the company in writing; request the company provide written confirmation if they want you to maintain speed (they will not do so as it would make them complicit). A collision caused by excessive speed in fog would expose the Master personally to criminal prosecution under the Merchant Shipping Act 1995.

B. Laytime runs regardless of weather. The Master has a contractual obligation to the charterer that overrides the discretionary safe speed provisions of Rule 6.

C. 16 knots is acceptable in 0.5nm visibility if radar is operational. Rule 6 permits any speed when the vessel has functioning radar and ARPA.

D. Reduce to 12 knots as a compromise — this satisfies both the charterer's commercial requirements and a reasonable safe speed interpretation.

A. Criminal liability exposure for the Master: (1) Merchant Shipping Act 1995 Section 58 — Conduct endangering ship or persons on board: "A master of, or seaman employed in, a United Kingdom ship who, while on board the ship, does any act which causes or is likely to cause the loss or destruction of or serious damage to his ship or the death of or serious injury to a person on board his ship is guilty of an offence." This applies where the Master failed in their supervisory duty; (2) MS Act 1995 Section 100 (manslaughter) and Gross Negligence Manslaughter (common law) — if injury leads to death, the Master may face manslaughter charges if their conduct was grossly negligent; (3) ISM duty: failure to ensure adequate bridge watchkeeping and OOW supervision; (4) The Master is also exposed to personal P&I subrogation claims if found personally negligent. The fact that the OOW was technically compliant with lane navigation but not with COLREGs Rule 8 timing raises questions about bridge supervision and watchkeeping instruction under the Master's standing orders.

B. Criminal liability rests solely with the OOW who was on watch. The Master is not on the bridge and bears no responsibility for the OOW's actions under COLREGs.

C. No criminal liability arises from a collision in a TSS if the vessel was in the correct lane. TSS lane compliance provides a complete defence to any COLREGs prosecution.

D. Criminal liability only applies if the collision was deliberate. Negligent navigation is a civil matter resolved through P&I insurance, not criminal proceedings.