International distress signals at sea: overview

The list of distress signals is set out in Annex IV of the International Regulations for Preventing Collisions at Sea, COLREGs for short. Because ships of every nation follow these rules, a red flare means the same everywhere in the world: someone here is in distress and needs help.

The signals cover different situations. Radio reaches ships over long distances, even ones you cannot see. Light works mainly at night, smoke by day. Sound, such as continuous sounding of a fog horn, helps in poor visibility. Body signals work without any equipment, and emergency beacons report via satellite to rescue coordination centres.

One of these signals alone is enough to show distress. But combining several increases the chance that anyone notices at all – because a visual signal only works if someone happens to be looking.

On the radio, ‘MAYDAY’ is the distress word; it is spoken three times and means immediate danger to life or to the vessel. On VHF marine radio, channel 16 is the international distress and calling channel. Many marine radios also have a button for digital selective calling that can send a distress alert with position. Depending on the country, marine radio requires an operator's certificate – check local rules.

Visual signals: red hand flares or parachute rockets with a red light, orange smoke by day, SOS with a lamp (three short, three long, three short) and slowly, repeatedly raising and lowering both arms stretched out to the sides. Everyone on the water should know the arm signal in particular, including in a kayak or on a SUP.

Audible signals: continuous sounding with a fog horn, or SOS as a sound signal. On small craft a whistle worn on the body is a simple tool. Electronic signals: an activated emergency beacon, for example a maritime distress beacon or a personal locator beacon, raises the alarm via satellite.

The order in an emergency: first the distress call by radio or phone, so that rescue centres know. Use visual signals when ships or aircraft are in sight. Pyrotechnics such as flares and rockets only last a short time; do not use them up ‘on spec’, but set them off when someone can see them.

Which equipment must or should be on board depends on boat type, sailing area and country. At least a whistle, a light and a phone in a waterproof case belong on small boats too. Depending on the waters, marine radio, a beacon and pyrotechnics are added. Water sports associations and authorities provide information on the requirements in your country.

Before every trip, check expiry dates, batteries and access: signalling equipment must be reachable even if the boat capsizes. Whatever is deep in a locker is no use in the water. On kayaks, canoes and SUPs, the most important items should be worn on the body or on the buoyancy aid.

Pyrotechnic signals are dangerous: they get very hot, can cause burns and start fires. Use, store and dispose of them only according to the manufacturer's instructions and local rules. Do not set off expired signals yourself or throw them in the rubbish – ask about official return points. Depending on the country, certain pyrotechnics require training or authorisation.

Distress signals are exclusively for real distress. A false alarm, such as an accidentally activated beacon or a flare set off for fun, triggers a real search. If an alarm has been raised by mistake, report it immediately to the coastguard or rescue centre so that nobody goes out unnecessarily.

If you see distress signals on the water from land, do not swim or go out yourself. Call the local emergency number (112 in the EU) or the coastguard, describe what you saw and where, and keep the spot in sight until help arrives. You are then the most important witness.

Alongside COLREGs there is the International Convention for the Safety of Life at Sea (SOLAS). Among other things it governs which safety equipment large ships must carry. Leisure craft, on the other hand, are subject to their own rules depending on the country.

The complete list of distress signals is only found in Annex IV of the COLREGs itself; this overview names the most important ones. Anyone who is regularly on the water should take a course, for example in marine radio or safety on board. That is also where you learn to handle pyrotechnics safely.

A common misunderstanding: friendly waving with one hand is often taken as a greeting, not a call for help. Anyone who needs help therefore uses the clear signal of both outstretched arms, slowly raised and lowered.