Foghorn and Reduced Visibility

When visibility drops, you often hear first what you can no longer see. Foghorns, fog bells and the mandatory sound signals under the Collision Regulations (COLREGs) become the central orientation system – alongside radar, AIS and GPS. For regatta sailors: fog is not merely a weather phenomenon, but a signal and safety management issue. Those who know fog signals, sound signals and the boundary between nautical seafaring and racing rules do not sail blindly through the gray zone, but act in a structured, rule-compliant way with reduced risk.

Why Foghorns and Sound Signals Are Decisive in Regatta Sailing

In reduced visibility, the visual references that regatta sailors normally rely on disappear: marks, competitors, committee boat, wind lines on the water surface. What remains are auditory information, electronic navigation and clear procedures. The foghorn is not an optional luxury – on many venues it is mandatory equipment and the acoustic backbone of collision avoidance.

The meteorological fundamentals on fog types, visibility ranges and forecasting can be found in the article Fog and Reduced Visibility. This guide focuses on sound signals, fog signals and the interaction with race management.

Three Levels You Must Distinguish

1. Nautical warning and sound signals under COLREGs and national regulations (collision avoidance, area warnings).
2. Regatta signals from the race committee (postponement, abandonment, fog mode) – see also Storm Flags and Race Abandonment.
3. Crew-internal communication (radio, hand signals, fixed commands in zero visibility).

Fog Signals and Area Warning Signals

At coasts, lighthouses, locks and some regatta venues, stationary fog signals provide information about hazards and area conditions. Sailors typically hear:

• Long sustained tones (foghorn): warning of fog or reduced visibility in the area
• Short tones at intervals: light or mark that is acoustically substituted in zero visibility
• Bell strokes on inland waterways: navigation marks or bridges in fog

On inland lakes and river regattas, club-specific or official systems often apply. Details are in the Notice of Race and area handbooks – compare Inland Waterway Particularities.

Acoustic Area Signals at a Glance

Mandatory Sound Signals under COLREGs in Fog

As soon as visibility is restricted – internationally commonly from visibility ranges below about 1000 metres – all vessels must give certain sound signals. Sailing boats are no exception, not even during a regatta.

Practice on Regatta Sailing Boats

1. Carry a foghorn – fixed mounted or as a hand horn; on dinghies often mandatory per class rules or SI.
2. Practise signal interval – crew member with timer or fixed rhythm; do not wait until zero visibility to start.
3. Observe engine signal – anyone using the engine for manoeuvring or after abandonment changes the sound signal.
4. Listen instead of look – direction and distance of tones are unreliable in fog; reduce speed.

Foghorn On Board: Equipment and Maintenance

Regatta sailors need reliable sound devices. Requirements vary by boat class, venue and Sailing Instructions.

Typical Equipment

• Electric foghorn (12 V or battery): check range and duration before regatta week
• Hand horn with compressed air cartridge: backup on dinghies and small boats
• Whistle: supplement for short close-range signals, not a COLREGs substitute
• Radio with DSC: supplement to audible signals – see AIS and Collision Avoidance

Pre-Start Checklist with Fog Forecast

• Foghorn functional (test tones on the water)
• Spare battery or cartridge on board
• Race committee radio channel noted and monitored
• GPS/plotter with current course and waypoints – see GPS, Plotter and Classic Navigation
• AIS receive and transmit ready (if required)
• Crew briefed: sound signal rhythm and fog mode
• Life jackets worn at all times
• Speed limit per SI clarified

Race Management in Reduced Visibility

The race committee often reacts to fog earlier than to wind problems. Typical measures:

1. Postponement (AP) – start delayed until visibility or wind conditions improve.
2. Course relocation – closer to shore or into a less fog-prone zone, if permitted by SI.
3. Abandonment of race in progress – signal N over H or equivalent; see Abandonment and Postponement.
4. Fog mode in the SI – reduced maximum speed, mandatory radio check, prohibited spinnaker sets.

Race Committee Responds to Fog

Scoring Consequences

If a race is abandoned due to fog, the scoring rules of the SI apply: often BFD or DNF provisions are excluded, instead ZFP (counts as participation without place) or a re-sail. Details are in the Notice of Race – do not improvise.

Navigation and Collision Avoidance in Fog

Visual navigation fails; electronic and acoustic means move to the foreground.

Priority Order

1. Reduce speed – more reaction time than any technology
2. Give sound signals – COLREGs-compliant and regular
3. AIS and radar – detect other vessels early
4. GPS/plotter – own position and course limits
5. Radio – coordinate position and manoeuvres with race committee

When fleets are close together, the risk of silent collisions increases – boats hear each other but cannot see each other. Professionals often sail wider then, accept layline losses and forgo aggressive covering tactics.

Visibility Range and Collision Risk

Crew Procedure: Fog Mode on Regatta Sailing Boats

A fixed crew procedure prevents chaos when visibility suddenly drops.

Role Distribution (Keelboat Example)

Numbered Procedure Checklist When Visibility Drops

1. Start foghorn signal (1 long + 2 short when sailing).
2. Reduce speed by at least 30–50 percent.
3. Radio check with race committee and coach boat if applicable.
4. Activate AIS alarms; radar if available.
5. Stop spinnaker/gennaker planning if visibility is critical.
6. All crew members in life jackets.
7. Fixed commands: "Boat ahead port/starboard", "mark acoustically".
8. If visibility below SI limit: abandon race or proceed to assembly position.

Foghorn and Racing Rules of Sailing

In competition, the RRS still apply – but COLREGs and area law take precedence for safety. Rule 2 (Fair Sailing) and the safety rules of the SI prohibit continuing to sail aggressively in life-threatening visibility.

Important points:

• Rule 10 (port-starboard) applies even in zero visibility – anyone who cannot see the other boat must still give way when auditory or AIS indications are present.
• Protests in fog are difficult to pursue – prevention beats protest.
• Support fleet and committee boat often give additional radio instructions.

More on the overarching topic: Nautical Warning Signals.

Frequently Asked Questions on Foghorns and Sound Signals

Sound signals during an ongoing regatta?

Yes, COLREGs always apply – even during a race.

Whistle instead of horn?

No. A whistle does not replace a COLREGs-compliant foghorn.

Start in fog?

Only if Sailing Instructions and safety situation permit.

Collision despite signal?

Activate emergency protocol, use radio, request help.

AIS instead of horn?

AIS supplements navigation, it does not replace sound signals under COLREGs.

Typical Mistakes and How to Avoid Them

• Foghorn only at zero visibility: Test and brief crew already when visibility is under 2000 m.
• Full regatta speed: Observe SI limits and common sense.
• Forgetting sound signals: Assign a separate crew member for horn interval.
• Confusing area signals with regatta AP: Use race committee radio as primary source.
• No course limits in plotter: Load waypoints and boundaries before the start.

Activating Fog Mode – Workflow

Summary for Regatta Sailors

Foghorn and reduced visibility demand discipline instead of heroics. Those who read COLREGs sound signals, area warning signals and race management in parallel reduce collision risk. Prepare in the morning briefing and switch to fog mode early.

Related Topics

• Fog and Reduced Visibility
• Storm Flags and Race Abandonment
• Nautical Warning Signals
• AIS and Collision Avoidance
• GPS, Plotter and Classic Navigation

Last updated: July 4, 2026