Before you spearfish — this comes first
- Get proper instruction before you spearfish. A recognised freediving or spearfishing course teaches the things that actually kill people in this sport, and reading about them is not the same as being taught them.
- Dive with a buddy, and dive one up, one down — one diver in the water, one on the surface watching them, every dive. A breath-hold blackout is silent and gives no warning; a watching buddy is the difference between an incident and a fatality.
- Stay inside your own training and experience. Depth and breath-hold times are personal, they change day to day, and nobody else's numbers apply to you.
- Understand the conditions before you enter the water: visibility, current, swell, tide, boat traffic and your exit. Conditions decide whether a dive is reasonable far more often than skill does.
- Use equipment you have been shown how to use, check it before every session, and be visible — a marked float and line are how boat traffic knows you are there.
- Never extend a dive for a fish. No catch is worth pushing a breath-hold, and the urge to take one more second is exactly what a blackout feels like from the inside — which is to say, like nothing at all.
How fish behave towards a diver
Explainer · Last reviewed 2026-08-10
A diver reads as a large predator, which is why stillness works, direct approach does not, and heavily dived ground behaves differently.
Safety
Fish welfare — Can cause injury needing treatment
Reading behaviour is what lets a diver get close, and getting close is also what produces shots taken on an animal that has not been identified or sized. A fish approaching confidently is easy to shoot and no easier to identify.
What reduces it: Use the closeness behaviour buys to identify and size the fish rather than to shorten the decision. Uncertainty means the shot is not taken, and a fish that comes in once will usually come in again.
Encounters with marine life — Can cause injury needing treatment
Behaviour that reads as curiosity in one animal reads as a defensive display in another, and a diver who has learnt to approach fish closely will eventually apply that to something that objects — a moray in a hole, a large territorial fish on a nest, or a shark investigating.
What reduces it: Give animals a way out and do not corner them. Leave the water rather than manage a persistent encounter, and treat any animal that changes its behaviour towards you as a reason to move.
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.
Underwater, a spearfisher is a large, slow, noisy predator. Everything fish do around one follows from that, and understanding it is what separates divers who see fish from divers who see fish leaving.
FLIGHT DISTANCE is the range at which a fish moves away, and it is not fixed. It varies by species, by how heavily the ground is dived, by visibility, and — most usefully — by what the diver is doing. A diver swimming directly at a fish, on the surface, silhouetted, has a large flight distance. The same diver settled quietly on the bottom has a much smaller one.
DIRECT APPROACH READS AS HUNTING. Swimming straight at a fish, and looking straight at it, are both predator behaviours that fish are equipped to detect. Approaching obliquely, and not fixing on the fish, measurably changes the response — which is one of the few pieces of practical technique that has an obvious mechanism behind it.
CURIOSITY is the exploitable counterpart. Many species will approach something novel and stationary, particularly wrasse and several reef genera, and that is what aspetto uses.
And ground has a MEMORY. Fish that have been shot at, or have seen a diver, behave differently for some time afterwards. A spot dived every weekend is a different spot from one dived twice a year, and no amount of technique compensates.
What this means for selective harvest
The behavioural picture has a conservation consequence that is worth drawing out, because it is specific to spearfishing and rarely stated.
Spearfishing is the most selective way of taking a fish that exists. The diver sees the animal before committing — species, size, condition — and can decline. There is no bycatch, no undersized fish taken by accident, and no fish released with a hook injury of unknown consequence.
But selectivity is a capability, not a virtue in itself, and what it is used FOR decides whether it is good or bad. A diver who selects for the largest fish on a piece of ground is selecting, in many species, for the oldest individuals — and in protogynous species such as many wrasse and several reef genera, for the breeding males specifically. Doing that repeatedly on site-attached fish with a small home range has a structural effect on that population that the same weight of fish taken indiscriminately would not.
The useful conclusion is not that big fish should never be taken. It is that the selectivity which makes spearfishing defensible is the same capability that makes it possible to do something quite targeted and quite damaging, and that the diver is the only control in the system. Nothing else in the method will stop them.
Scientific evidence
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
- FishBase: a global information system on fishes — Froese, R. and D. Pauly, eds. — FishBase Consortium (Scientific institute)Relied on for: That protogynous hermaphroditism occurs in wrasse and other reef-associated genera, such that the largest individuals in a population are disproportionately male.States this directlyPassage read and verified
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: That gear selectivity is a component of fishery sustainability assessment and that the effect depends on what is selected.FishingHQ's interpretation of what it saysCitation checked — the work exists and is described correctly
Where to go next
Fish this applies to
What these connections rest on (1)
Scientific evidence — 1 connection
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Ballan wrasse
A behavioural and reproductive-biology claim with a direct conservation consequence, which is precisely why it is held to a scientific standard rather than left as practitioner lore.
- FishBase: a global information system on fishes — Froese, R. and D. Pauly, eds. — FishBase Consortium (Scientific institute)Relied on for: Protogynous hermaphroditism in Labrus bergylta, such that larger individuals are disproportionately male.States this directlyPassage read and verified
- Good Fish Guide — Marine Conservation Society (Conservation authority)Relied on for: That the size and sex structure of a local population is material to whether taking large individuals is sustainable.FishingHQ's interpretation of what it saysCitation checked — the work exists and is described correctly
Where it matters
- Aspetto (waiting)Aspetto works because a stationary diver stops reading as a predator and curious species come to inspect. The technique is an application of the behaviour, not a trick.
- SpearfishingReading behaviour is how a diver gets within range at all, which is the technique the whole discipline consists of.
- StalkingApproach angle is the whole technique: a diver swimming straight at a fish reads as a predator hunting, and one drifting obliquely past frequently does not.
What these connections rest on (3)
Practitioner consensus — 2 connections
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.
Aspetto (waiting)
A behavioural explanation stated at practitioner level, with the underlying biology supported separately on the concept record.
- BSAC diving safety guidance and annual incident report — British Sub-Aqua Club (Water-safety or diver-training authority)Relied on for: General in-water conduct and its effect on marine life encounters.Citation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated practitioner accounts of fish response to stationary divers.Citation checked — the work exists and is described correctly
Stalking
A behavioural claim at practitioner level, with the underlying biology supported separately on the concept record.
- BSAC diving safety guidance and annual incident report — British Sub-Aqua Club (Water-safety or diver-training authority)Relied on for: General in-water conduct and its effect on marine life encounters.Citation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated practitioner accounts of fish flight response to divers.Citation checked — the work exists and is described correctly
Authoritative guidance — 1 connection
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 record 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
Gear this affects
What these connections rest on (1)
Practitioner consensus — 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.
Pole spears and Hawaiian slings
Approach behaviour is the skill the method depends on, and it is taught as such.
- BSAC diving safety guidance and annual incident report — British Sub-Aqua Club (Water-safety or diver-training authority)Relied on for: Diving body guidance on behaviour and awareness underwater.Background and mechanism onlyCitation checked — the work exists and is described correctly
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: Practitioner accounts of approaching fish while breath-hold diving.States this directlyCitation checked — the work exists and is described correctly