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.
Fitness to dive: health, medication and when not to
Explainer · Last reviewed 2026-08-27
Whether somebody is fit to breath-hold dive is a medical assessment made by a doctor for an individual — and the categories of condition that require one are worth knowing before a course, not after a problem.
Safety
Barotrauma and pressure injury — Can cause injury needing treatment
Diving with congestion or an unassessed ear, sinus or respiratory condition leads to failed equalisation and to the injuries that follow forcing it, and some conditions carry a risk of loss of consciousness in water.
What reduces it: A medical assessment by a doctor with diving-medicine training before starting, particularly for respiratory, cardiovascular, ENT and neurological history; not diving with congestion or recent illness; and treating any day the diver feels wrong as a day to stop.
This record explains a process. It does not perform it, and nothing here clears anybody to dive or advises anybody not to.
WHY IT MATTERS MORE IN BREATH-HOLD DIVING THAN PEOPLE ASSUME. A breath-hold diver experiences large pressure changes, significant cardiovascular loading, cold exposure and deliberate hypoxia, often far from help and while carrying responsibility for somebody else's safety. Conditions that are unremarkable on land can matter here through mechanisms that are not obvious, and the reasoning is different from that used for compressed-air diving.
THE CATEGORIES THAT REQUIRE ASSESSMENT. This is a map of where to ask, not a checklist to self-administer.
RESPIRATORY. Anything affecting the airway or lung, including asthma and any history of lung injury or air trapping. Breath-hold diving involves large lung volume changes with pressure.
CARDIOVASCULAR. The diving response itself alters heart rhythm, and immersion, cold and exertion combine in ways that matter for anybody with a heart condition or a family history of arrhythmia.
EAR, NOSE AND SINUS. The commonest limiting factor. Perforation, surgery, chronic congestion and structural problems all bear directly on equalisation, and forcing equalisation is how the injuries happen.
NEUROLOGICAL. Any history of seizure, loss of consciousness or blackout from any cause is significant in an activity whose defining hazard is losing consciousness in water.
MEDICATION, which matters through its EFFECTS rather than the condition treated — sedation, altered heart rate, altered thermoregulation, altered fluid balance.
AND THE TEMPORARY ONES, which people take far less seriously than the permanent ones and which cause more incidents: a cold or blocked sinuses, recent illness, recent injury, dehydration, alcohol the night before, poor sleep, and simple fatigue.
What this record does not do, stated plainly
IT DOES NOT ASSESS ANYBODY. FishingHQ cannot tell a reader whether they are fit to dive, and no page can. Fitness to dive is an individual clinical judgement made by a doctor with diving-medicine training, taking into account the person and the diving they intend to do.
IT NAMES NO CONDITION AS DISQUALIFYING and none as safe. The same diagnosis produces different answers in different people, and a general statement in either direction would be wrong for somebody reading it.
IT PUBLISHES NO THRESHOLDS — no ages, no measurements, no test results.
WHAT IT DOES SAY. That the assessment exists, that recognised training organisations require a health declaration and in some cases a medical, that the categories above are the ones that trigger a proper conversation, and that the conversation is worth having before a course rather than after a problem.
AND WHERE TO ASK. A doctor with diving-medicine training rather than a general appointment, because the reasoning is specialised and a GP with no diving background may reasonably not know it. National diving medical bodies maintain lists of such doctors, and training organisations will point people to them.
ONE THING WORTH SAYING ANYWAY. Nobody should be diving on a day they feel wrong, whatever their medical status. That is not a clinical judgement, it is the same rule as the rest of this family: the session can be abandoned and stopping is a complete answer.
Authoritative guidance
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- UK Diving Medical Committee guidance on medical standards for divers — UK Diving Medical Committee (Water-safety or diver-training authority)Relied on for: That fitness to dive is assessed individually by a doctor with diving-medicine training, and the categories of condition that require specific assessment.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: Diving medicine guidance on health considerations for breath-hold divers and on when medical advice is required.States this directlyPassage read and verified
- AIDA International freediving education and safety standards — AIDA International (Water-safety or diver-training authority)Relied on for: That recognised freediving education standards include health declaration requirements before training.Background and mechanism onlyCitation checked — the work exists and is described correctly
The day-to-day version, which is where most incidents live
Long-term medical fitness is assessed once and revisited occasionally. Fitness on the day is assessed every time, by the diver, and it is the one that actually varies.
WHAT CHANGES A DIVER'S CAPACITY BETWEEN ONE WEEK AND THE NEXT.
CONGESTION. A cold, hay fever or a blocked sinus makes equalisation difficult or impossible, and the injuries in this discipline come from forcing it. Decongestants that wear off at depth are a recognised way to make this worse rather than better.
FATIGUE AND SLEEP. Both affect breath-hold tolerance and, more importantly, judgement.
DEHYDRATION, which is easy to arrive at after a hot drive and a morning in a wetsuit, and which affects cardiovascular tolerance and cramp.
ALCOHOL, including the night before, through sleep quality, dehydration and thermoregulation.
RECENT ILLNESS, particularly anything respiratory, and for longer than people expect.
SIMPLY NOT HAVING BEEN IN THE WATER FOR MONTHS. Capacity declines and confidence does not, which is a bad combination in an activity where the margin is invisible.
THE RESPONSE IS ALWAYS THE SAME and it is the cheapest intervention available in this discipline: dive shallower, dive shorter, or do not dive. A session abandoned costs a day. This vertical is unusually consistent about that because the alternative failure is not recoverable.
Authoritative guidance
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- DAN guidance on freediving safety, hypoxia and shallow-water blackout — Divers Alert Network (Water-safety or diver-training authority)Relied on for: Guidance on equalisation, congestion, and the physiological factors affecting breath-hold divers on a given day.States this directlyPassage read and verified
- UK Diving Medical Committee guidance on medical standards for divers — UK Diving Medical Committee (Water-safety or diver-training authority)Relied on for: Guidance on temporary conditions and medication as they bear on fitness to dive.States this directlyCitation checked — the work exists and is described correctly
Where to go next
Where it matters
What these connections rest on (1)
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.
- DAN guidance on freediving safety, hypoxia and shallow-water blackout — Divers Alert Network (Water-safety or diver-training authority)Relied on for: Freediving and breath-hold spearfishing safety practice, including the supervision requirement that applies across the discipline rather than to particular equipment.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 discipline definition set out by the international underwater federation.States this directlyCitation checked — the work exists and is described correctly
A safety gap the family never asked: it covered what happens in the water and never who should be in it.
- UK Diving Medical Committee guidance on medical standards for divers — UK Diving Medical Committee (Water-safety or diver-training authority)Relied on for: That fitness to dive is an individual clinical assessment, and the categories of condition that require one.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: Diving medicine guidance on health considerations for breath-hold divers.States this directlyPassage read and verified
Related reading
- Breath-hold physiology for spearfishersLarge pressure changes, cardiovascular loading, cold and deliberate hypoxia — the four demands that make medical fitness a specific question here.
- Equalisation and pressureEar, nose and sinus problems are the commonest limiting factor, and the injuries come from forcing equalisation rather than stopping.
What these connections rest on (2)
Authoritative guidance — 2 connections
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Breath-hold physiology for spearfishers
Why the reasoning differs from that used for compressed-air diving.
- DAN guidance on freediving safety, hypoxia and shallow-water blackout — Divers Alert Network (Water-safety or diver-training authority)Relied on for: Diving medicine guidance on breath-hold physiology, hypoxic blackout, cold exposure and supervision.States this directlyPassage read and verified
Equalisation and pressure
The specific mechanism behind the most frequent fitness-to-dive question.
- UK Diving Medical Committee guidance on medical standards for divers — UK Diving Medical Committee (Water-safety or diver-training authority)Relied on for: That fitness to dive is an individual clinical assessment, and the categories of condition that require one.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: Diving medicine guidance on health considerations for breath-hold divers.States this directlyPassage read and verified
Safety reading
What these connections rest on (1)
Authoritative guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Training and courses
Where the assessment normally happens, and the reason to have it before a course.
- AIDA International freediving education and safety standards — AIDA International (Water-safety or diver-training authority)Relied on for: That recognised freediving education is structured and assessed, and includes in-water rescue.States this directlyCitation checked — the work exists and is described correctly
Sources for this page
- UK Diving Medical Committee guidance on medical standards for divers — UK Diving Medical Committee (Water-safety or diver-training authority)Relied on for: Medical standards and assessment for divers.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: Diving medicine guidance for breath-hold divers.States this directlyPassage read and verified
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