While on watch in fog, you hear the following sound signals from ahead: one prolonged blast every two minutes. Then you hear two prolonged blasts every two minutes. Identify both signals and describe your response under COLREGs.

A. IDENTIFICATION OF SOUND SIGNALS: ONE PROLONGED BLAST every 2 minutes or less: A vessel under way making way (COLREGs Rule 35(a)). TWO PROLONGED BLASTS every 2 minutes or less: A vessel under way but stopped — making no way through the water (COLREGs Rule 35(b)). RESPONSE AS OOW: (1) REDUCE TO SAFE SPEED: Rule 19(b) — in or near restricted visibility, proceed at a safe speed adapted to the prevailing circumstances; (2) STOP ENGINES AND LISTEN if signal appears to be forward of the beam and close range (Rule 19(e)); (3) USE RADAR: commence radar plotting/ARPA tracking of the detected vessel; (4) CALL MASTER if not already on bridge; (5) POST LOOKOUT: both visual and audible — Rule 5; (6) SOUND OWN SIGNAL: own vessel if underway making way — one prolonged blast every 2 minutes; (7) Do NOT alter towards the signal — Rule 19(d)(ii): avoid alteration to port for a vessel forward of beam; (8) RECORD in deck log: time heard, bearing, approximate range (if radar contact), actions taken. Additional fog signals: three blasts (long-short-short) every 2 minutes = vessel not under command, restricted in ability, constrained by draught, at anchor, fishing, towing.

B. One prolonged blast is a vessel turning to port. Two prolonged blasts is a vessel turning to starboard. These are manoeuvring signals and apply in all visibilities.

C. These are anchor signals not underway signals. A vessel sounding one prolonged blast is at anchor. Two prolonged blasts means the anchor is aweigh.

D. In restricted visibility, sound signals do not carry reliable directional information. Ignore sound signals and rely solely on radar for collision avoidance in fog.

A. IMO STANDARD MARINE COMMUNICATION PHRASES (SMCP 2001): The SMCP is an IMO publication (Resolution A.918(22)) providing standardised English phrases for maritime communications. LEGAL BASIS: SOLAS Chapter V, Regulation 14 requires that officers in charge of a navigational watch on ships required to carry a radio installation shall be proficient in the use of English. The SMCP provides the standardised language to fulfil this requirement. WHEN MANDATORY: (1) VHF bridge-to-bridge communications for collision avoidance; (2) Communications with Vessel Traffic Services (VTS) — initial call, position reports, intentions; (3) Distress, urgency and safety communications on Channel 16; (4) Communications with pilots during embarkation and passage; (5) Port authority and harbour control communications; (6) SAR coordination communications; (7) Communications with other vessels for manoeuvring in restricted waters. STRUCTURE OF SMCP: phrases are organised by function — external communications (VHF), internal ship communications, and safety-related phrases. Responses use standard acknowledgements: "I read you", "Stand by", "Say again", "Received". KEY PRINCIPLE: English is the working language of international maritime communications — if neither party is a native English speaker, both must use SMCP rather than their own language.

B. SMCP are voluntary guidelines produced by IMO. They are only recommended practice and SOLAS does not require their use — captains may use any language agreed between the two vessels.

C. SMCP apply only to communications with shore-based VTS. Ship-to-ship communications may use any mutually understood language including the officers' native languages.

D. SMCP are required only for passenger vessels. Cargo ship officers must be proficient in English but are not required to follow the standardised SMCP format.

A. SMCP COLLISION AVOIDANCE CALL — CORRECT APPROACH: Initial call on Ch 16 (then switch to a working channel, typically Ch 13 or 16): "Vessel bearing [bearing] from me, this is [vessel name] on VHF channel [xx], over." After contact: "I am the stand-on vessel. I intend to maintain my course and speed. Please confirm your intentions, over." OR if you are the give-way vessel: "I am the give-way vessel. I intend to alter course to starboard [or slow down] to pass astern of you. Do you agree? Over." KEY SMCP PHRASES: "I intend to alter course to starboard/port", "I am altering course to starboard/port", "I intend to stop my engines", "Please indicate your intentions." RISKS OF VHF COLLISION AVOIDANCE: (1) VHF agreements are NOT a substitute for COLREGs action — the give-way vessel must act in good time regardless of VHF exchange; (2) VHF agreements can create false confidence — the other vessel may not follow through; (3) Use call sign or vessel name to ensure you are speaking to the correct ship — "vessel ahead" is ambiguous; (4) Rule 8 requires action to be positive, taken in ample time — do not delay COLREGs action waiting for VHF response; (5) Document the exchange in the deck log.

B. Call the vessel on Ch 16 and agree to both alter to starboard. Once agreed by VHF, both vessels should proceed according to the agreement and no formal COLREGs action is needed.

C. VHF should never be used for collision avoidance — it creates legal liability by demonstrating awareness of the risk before action was taken. Use radar and take COLREGs action silently.

D. Use any language common to both bridges. SMCP only apply to VTS communications. Ship-to-ship collision avoidance VHF calls have no standardised format requirement.