Buoyancy that feels wrong
Explainer · Last reviewed 2026-08-19
Struggling to descend and sinking too readily are the same problem in opposite directions, and one of them is dangerous — which is why the fix is a buoyancy check in the water rather than a number from a table.
Safety: shallow water blackout and breath-hold loss of consciousness — can cause serious injury or death.
Never dive alone, dive one up one down, and never extend a dive for a fish.
Shallow water blackout and breath-hold loss of consciousness — Can cause serious injury or death
An overweighted diver is negatively buoyant at the surface, must work hardest to ascend when oxygen is lowest, and sinks rather than floating if they lose consciousness.
What reduces it: Checking buoyancy in the water rather than using a formula, erring light, re-checking on any change of suit or water, and a quick-release belt worn over everything.
Buoyancy that feels wrong is almost always a weighting problem, and it matters because the correct answer is not symmetrical: being slightly light is inconvenient, and being heavy can be fatal.
TOO BUOYANT feels like fighting to get down, finning hard through the first few metres, and arriving at the bottom already breathless. It wastes oxygen at exactly the moment the dive is starting, and it usually happens with a new or thicker suit.
TOO HEAVY feels easy — that is the trap. Descent is effortless, the diver reaches the bottom relaxed, and everything seems better. What has actually happened is that the diver is now negatively buoyant at the surface, has to work to ascend at the point their oxygen is lowest, and will sink rather than float if they lose consciousness.
Overweighting is a documented contributor to freediving deaths. It is the correction beginners make when descending feels hard, and it feels like an improvement.
THE CHECK, NOT THE NUMBER. Correct weighting is verified in the water: at the surface with lungs comfortably full, a diver should float readily; at the depths they intend to fish they should not have to fight to come up. That check accounts for suit thickness and age, body composition, salinity, and the depth being dived — none of which a formula knows.
AND IT CHANGES. A new suit, an old suit that has compressed with age, fresh water instead of salt, or a change in the depth being fished all require re-checking.
Why FishingHQ gives no weighting figure
This is the page a reader most wants a number on, and the number is the dangerous thing to give.
Correct weight depends on suit thickness, suit age and neoprene type, fit, body composition, lung volume, fresh or salt water, and the depth being dived. Two people in the same suit legitimately need different amounts. A calculator producing a single figure would carry the authority of arithmetic and the accuracy of a guess, and its failure mode is a diver who is overweighted and believes a tool told them it was safe.
So the guidance is a procedure: check in the water, with a buddy, at the start of a session, and again whenever the suit or the water changes. **Err light.** A diver who is slightly underweighted works a little harder to descend. A diver who is overweighted may not come up.
The other half is the belt. Whatever the weight, it must release with one hand under load, be worn over everything, and be reachable — because the situation it exists for is one in which somebody is trying to get an unconscious diver to the surface.
Official guidance — why, and the sources (2)
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- AIDA International freediving education and safety standards — AIDA International (Water-safety or diver-training authority)Relied on for: Freediving education on buoyancy checking in water and weighting for positive surface buoyancy.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: Guidance identifying overweighting as a contributory factor in freediving incidents.States this directlyPassage read and verified
Safety
Shallow water blackout and breath-hold loss of consciousness is set out at the top of this page, where it cannot be missed.
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.
Where to go next
Where it matters
Related reading
How this compares
Sources and evidence
- 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 on weighting and buoyancy.States this directlyPassage read and verified
Why the 4 connections on this page are here, and the sources
Where it matters
Official 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 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
Related reading
Official guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Wetsuits, fins and masks for spearfishing
What triggers a re-check.
- AIDA International freediving education and safety standards — AIDA International (Water-safety or diver-training authority)Relied on for: Freediving education on buoyancy checking in water and weighting for positive surface buoyancy.States this directlyCitation checked — the work exists and is described correctly
How this compares
Official guidance — 2 connections
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Depth as an environmental variable
Why one weighting cannot be right everywhere.
- AIDA International freediving education and safety standards — AIDA International (Water-safety or diver-training authority)Relied on for: Freediving education on buoyancy checking in water and weighting for positive surface buoyancy.States this directlyCitation checked — the work exists and is described correctly
Weighting and buoyancy in spearfishing
The mechanics record and the symptom a beginner actually reports.
- AIDA International freediving education and safety standards — AIDA International (Water-safety or diver-training authority)Relied on for: Freediving education on buoyancy checking in water and weighting for positive surface buoyancy.States this directlyCitation checked — the work exists and is described correctly
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