Surface marking and signalling
Tackle · Last reviewed 2026-08-10
How a diver is seen by boats and found by their own — the equipment whose entire function is to work on the worst day rather than the average one.
Safety: boat traffic and being seen — can cause serious injury or death. 5 more points apply here.
Never dive alone, dive one up one down, and never extend a dive for a fish.
- Category
- Spearfishing equipment
A person in the water is close to invisible. From a boat at any speed, in any chop, with any glare, a head is nothing. This is the single most consistently underestimated fact in spearfishing, and it is why surface marking is equipment rather than an accessory.
There are two separate problems and they need different answers.
BEING SEEN BY OTHER VESSELS is solved by a large, brightly coloured float carrying a flag, kept close to the diver rather than trailing. It is worth understanding clearly that a dive flag does not create a legal exclusion zone in most places — what it obliges an approaching vessel to do varies by country and many skippers do not know the rule at all. The flag improves the odds; it does not confer protection, and diving as though it did is a mistake.
BEING FOUND BY YOUR OWN PEOPLE is a different problem with different tools. A whistle carries much further than a shout and costs nothing. A signalling mirror is visible for miles in sun. A brightly coloured surface marker that can be inflated and held up changes a diver from a dot into a target. And in open water, something that transmits — a personal locator, a waterproof phone in a case — is the difference between being looked for and being found.
All of it is carried for a day that will probably not happen, which is precisely why it gets left behind.
What it does
Makes a diver's position visible to vessels on the surface, and makes a diver in difficulty findable by their buddy, their boat or a rescue service. The first is passive and continuous; the second is active and used once, which is why they are different pieces of equipment.
How to choose one
- Bigger and brighter than feels necessary. The float is sized for a boat at distance in chop, not for you looking at it.
- Keep the float CLOSE. A float fifteen metres behind you marks water you are not in, and the line is an entanglement and propeller hazard.
- Carry an audible signal — a whistle costs nothing and carries far past shouting range.
- Carry something that works when nobody is looking your way: a mirror in sun, a light in low visibility.
- Do not treat a flag as protection. Know what it does and does not oblige other vessels to do where you are.
What the numbers mean
FLOAT VOLUME, in litres, determines both visibility and whether the float will support a resting diver — the second is a safety function and is worth paying for. FLAG TYPE differs by region: the red-and-white diver-down flag and the blue-and-white International Code flag A are both in use, sometimes together, and the obligations attached to each vary by jurisdiction. FLOAT LINE length should relate to the depth being dived plus a margin, and no more — excess line in the water is the hazard. VISIBILITY AIDS are rated by how far they can be seen; a mirror in direct sun outperforms almost anything else and requires the sun.
Care, and how it fails
Inflatable floats develop slow leaks at seams and valves, which are invisible until the float is soft at the end of a session. Check inflation before every dive. Lines abrade where they meet the float and the diver. Whistles clog with salt — rinse and test them. Batteries in lights and locators die on a schedule that has nothing to do with when you last used them, so check them by date rather than by memory. The failure mode for all of this is discovering it does not work on the one occasion it was needed.
Safety
Never dive alone, dive one up one down, and never extend a dive for a fish. The full set of breath-hold essentials — training, the buddy system, conditions, equipment and visibility — is on the spearfishing safety page.
Boat traffic and being seen — Can cause serious injury or death
A diver at or near the surface is close to invisible from a vessel under way, and a boat that sees one at close range cannot stop or turn in the distance available. Propeller injuries are catastrophic and often fatal.
What reduces it: A large, conspicuous flagged float per diver, kept close. Surface with an arm raised and look up before breaking the surface. Choose ground away from channels and moorings. Understand that a flag improves the odds rather than conferring protection, and that what it obliges other vessels to do varies by country.
Worse when:
- Chop or glare, which hide a float as effectively as a head
- Busy inshore water in summer
- Where the diver is separated from their float
Drowning and immersion — Can cause serious injury or death
A diver separated from their boat or their buddy, without a means of signalling, is a person in open water who cannot be found. In any sea state this escalates quickly.
What reduces it: Carry an audible and a visual signal on your person rather than on the boat. A float with enough volume to rest on. Agreed recall signals before the first entry. Tell somebody ashore where you are and when you will be back.
Precautions that always apply here
- Never spearfish or freedive alone.
- Dive one up, one down: one diver down, one on the surface actively watching, every single dive.
- Tell somebody where you are going and when you expect to be back.
- Carry a charged phone in a waterproof case, or another means of calling for help.
Further safety reading
- Fishing alone — Signalling matters most when there is nobody nearby who would notice a problem, which is precisely when it is most often left behind.
- Surface markers and boat traffic — Signalling equipment is what a diver has when a boat has not seen the float, which is the situation the whole category exists for.
Check the rules before you fish
Fishing laws, bylaws, access rules, seasons, bait restrictions and permitted methods vary by location and can change. Check the current rules from the relevant authority and the water you intend to fish before fishing.
Check with:
- Current national or regional law for where you are fishing
- Current local bylaws
- The relevant fisheries authority
- The landowner, club or fishery whose water it is
- Any restrictions specific to the species or the method you intend to use
Where to go next
Where it is used
- SpearfishingA person in the water is close to invisible from a boat. This is equipment whose entire function is to work on the worst day rather than the average one, which is exactly why it gets left behind.
- Boat divingThe dive flag, the recall signal and the means of being seen from a vessel are the whole safety system of boat diving, and they are equipment rather than technique.
Understanding it
Instead of this
Sources and evidence
- BSAC diving safety guidance and annual incident report — British Sub-Aqua Club (Water-safety or diver-training authority)Relied on for: Surface marking practice for divers, the visibility problem a diver presents to vessels, and the use of dive flags.States this directlyCitation checked — the work exists and is described correctly
- RNLI water safety guidance: cold water shock and Float to Live — Royal National Lifeboat Institution (Water-safety or diver-training authority)Relied on for: Carrying a means of calling for help, telling somebody your plan, and the risk to a person separated in open water.States this directlyPassage read and verified
Why the 6 connections on this page are here, and the sources
Where it is used
Official guidance — 2 connections
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Spearfishing
A membership assertion rather than a topical one: this page teaches the discipline or its equipment, so the discipline's mandatory safety posture applies to it.
- CMAS technical and sporting standards for underwater activities — Confédération Mondiale des Activités Subaquatiques (Standards body)Relied on for: Breath-hold spearfishing as a defined discipline with its own technical, equipment and safety standards, set out by the international underwater federation.States this directlyCitation checked — the work exists and is described correctly
- DAN guidance on freediving safety, hypoxia and shallow-water blackout — Divers Alert Network (Water-safety or diver-training authority)Relied on for: That the safety requirements of breath-hold diving apply across the discipline rather than to particular equipment or techniques within it.States this directlyPassage read and verified
A safety-equipment claim sourced to diving and water safety authorities.
- BSAC diving safety guidance and annual incident report — British Sub-Aqua Club (Water-safety or diver-training authority)Relied on for: Surface marking practice for divers, the visibility problem a diver presents to vessels, and the use of dive flags.States this directlyCitation checked — the work exists and is described correctly
- RNLI water safety guidance: cold water shock and Float to Live — Royal National Lifeboat Institution (Water-safety or diver-training authority)Relied on for: Carrying a means of calling for help, telling somebody your plan, and the risk to a person separated in open water.States this directlyPassage read and verified
Boat diving
The method's dominant hazard is being invisible to a vessel, and this is the record that covers the equipment answering it.
- DAN guidance on freediving safety, hypoxia and shallow-water blackout — Divers Alert Network (Water-safety or diver-training authority)Relied on for: Breath-hold diving safety practice, including supervision, surface marking and the equipment the discipline depends on.Background and mechanism onlyPassage read and verified
Understanding it
Official guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Boat traffic, and being seen from the surface
Signalling equipment exists for this hazard and its rules are regional.
- BSAC diving safety guidance and annual incident report — British Sub-Aqua Club (Water-safety or diver-training authority)Relied on for: Diving safety guidance on surface marking, dive flags and vessel traffic.States this directlyCitation checked — the work exists and is described correctly
Instead of this
Official guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Dive floats and float lines
Diving body guidance treats marking and signalling as separate measures.
- BSAC diving safety guidance and annual incident report — British Sub-Aqua Club (Water-safety or diver-training authority)Relied on for: Guidance on surface marking and on signalling for assistance.States this directlyCitation checked — the work exists and is described correctly
What experienced anglers do — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Dive floats and float lines
A dependency between equipment, recorded because choosing one of these constrains the other. Convention, recorded as convention.
- DAN guidance on freediving safety, hypoxia and shallow-water blackout — Divers Alert Network (Water-safety or diver-training authority)Relied on for: Freediving safety guidance including weighting, positive buoyancy at the surface, the buddy system and the management of entanglement and equipment failure.States this directlyPassage read and verified
- CMAS technical and sporting standards for underwater activities — Confédération Mondiale des Activités Subaquatiques (Standards body)Relied on for: Breath-hold diving safety practice and equipment expectations set out by the international underwater federation.States this directlyCitation checked — the work exists and is described correctly
Safety reading
Official guidance — 2 connections
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Fishing alone
Water safety guidance on the additional precautions required when alone.
- RoSPA water safety information and UK accidental drowning statistics — Royal Society for the Prevention of Accidents (Water-safety or diver-training authority)Relied on for: Guidance on the risks of being alone near or in water.States this directlyPassage read and verified
Surface markers and boat traffic
Diving body guidance on visibility to surface traffic.
- BSAC diving safety guidance and annual incident report — British Sub-Aqua Club (Water-safety or diver-training authority)Relied on for: Guidance on being seen by boat traffic and on signalling.States this directlyCitation checked — the work exists and is described correctly
How FishingHQ labels evidence is explained in the evidence policy.