1.18 Sound Signals in Restricted Visibility (Rule 35)

Rule 35 Context for Master 100

Rule 35 governs sound signals in or near an area of restricted visibility, whether by day or by night. Restricted visibility (Rule 3) includes fog, mist, falling snow, heavy rain, sandstorms, or similar causes. Sound fog signals when you are in the reduced visibility or near it — clearing a fog bank at the harbor mouth still creates Rule 35 duties if vessels inside may hear or meet you.

These signals replace Rule 34 maneuvering blasts for vessels not in visual sight. Patchy fog that suddenly gives a visual at 200 yards can bring Rule 19 and, once in sight, Rule 34 into play — but pure fog exam items use one prolonged / two prolonged / prolonged + shorts / bell.

Pair Rule 35 with Rule 19, Rule 5 (hearing lookout), and Rule 6 (safe speed). A perfect whistle cadence at 18 knots into a whiteout still fails the seamanship story.

Power-Driven Vessels Underway

Making way vs not making way is the highest-yield pair. Sliding at 3 knots in neutral = still making way → one prolonged. No way on while still underway (not anchored/aground/made fast) → two prolonged. Kill headway to assess a radar contact and change the cadence when way is truly off.

Special-Status and Working Vessels — Prolonged + Two Short

Sound at ≤2-minute intervals one prolonged followed by two short if you are: NUC; RAM (underway or at anchor when RAM applies); CBD (International only); sailing; engaged in fishing (underway or at anchor); or towing/pushing another vessel.

Mnemonic: "special or sail or fish or tow → long-short-short." Ordinary passenger carriage does not earn this pattern.

Vessel being towed (if manned)

A manned vessel under tow — or the last manned vessel of a multi-vessel tow — sounds one prolonged + three short at ≤2-minute intervals, immediately after the towing vessel when practicable. Tug: prolonged + two short; manned barge: prolonged + three short. Unmanned barges do not sound.

Composite units

Pushed ahead and towed alongside, when rigidly connected as a composite unit, are treated as a power-driven vessel (one or two prolonged), not the tow pattern.

Pilot Vessels

A pilot vessel on pilotage duty may add an identity signal of four short blasts to her power-driven fog signals (making way or stopped). Do not confuse four shorts with danger (≥5 shorts, Rule 34 in-sight).

Anchored — Bell and Gong

At intervals of not more than 1 minute, ring the bell rapidly for about 5 seconds. Vessels ≥ 100 m: bell in the forepart, then gong rapidly ~5 s in the after part.

Optional warning: one short, one prolonged, one short (short–prolonged–short) to warn of position and collision possibility — not five shorts, not one prolonged alone.

Ordinary Master passenger craft at anchor: bell (and gong only if ≥100 m). NUC / RAM / fishing at anchor use the prolonged + two short pattern under the special-status rules rather than a simple bell-only picture on many exam items.

Aground

Give the anchor bell (and gong if required) plus three separate and distinct strokes on the bell immediately before and after the rapid ringing. May also sound an appropriate whistle signal. Pattern: stroke×3 → rapid ring ≈5 s → stroke×3. Do not confuse with the optional anchor short-prolonged-short whistle.

Under 12 m and Seaplanes

Vessels < 12 m need not give the full suite but shall make some other efficient sound signal at ≤2-minute intervals. A seaplane on the water may use power-driven signals or another efficient signal at ≤2 minutes.

Master Scenario: Fog on a Bay Tour

You Master a 58-foot inspected passenger vessel inbound in fog. Making way at bare steerage: one prolonged every ≤2 minutes, hearing lookout, radar, engines ready (Rule 19). Take all way off: switch to two prolonged. A sailing charter nearby: prolonged + two short. Pilot boat may add four short. Anchored yacht <100 m: bell ~5 s every ≤1 minute. Five short rapid blasts are not a Rule 35 fog cadence — treat as doubt/danger from a vessel in a visual close-quarters situation.

Recognition table

Exam Framing for Q100 (90%)

Match making way vs stopped; sail/fish/tow vs ordinary power; manned tow +3 short; pilot four short; anchor bell 5 s / 1 min; aground three strokes before and after; optional anchor warning short-prolonged-short. Interval traps swap 1 min (bell) with 2 min (whistle). Status traps assign passenger vessels the RAM fog signal without a Rule 3 RAM basis.