Decompression Sickness in Freediving: Taravana Explained

Freedivers can get decompression sickness (DCS), although it’s much rarer than in scuba diving. Decompression sickness in freediving happens when many dives to depth with short rests at the surface let nitrogen build up in the body faster than it can leave. Pearl divers in the Tuamotu islands of French Polynesia called the resulting illness taravana. Prevention is straightforward: long enough surface intervals, only a few deep, demanding dives per session, and no freediving after scuba on the same day.

How breath-hold divers absorb nitrogen

Air is roughly 78 per cent nitrogen. On a freedive, water pressure compresses the air in your lungs, raising the partial pressure of that nitrogen, and some of it dissolves into your blood and from there into your tissues. The deeper and longer the dive, the more dissolves. Pressure, depth and Boyle’s law explains the physics.

On the way up, the process reverses and nitrogen moves back out to be breathed away. After one dive, the amount is small and clears during your rest at the surface. The trouble starts when you dive again before it has cleared. Each dive adds a little more, and over a long session with short rests, your tissues can hold enough nitrogen to form bubbles when you surface. That is decompression sickness, the same condition scuba divers call “the bends”.

Taravana: what the Tuamotu pearl divers showed

Some of the clearest early evidence came from pearl divers in the Tuamotu archipelago. Doctors who studied them in the mid-20th century described divers who reportedly made dozens of dives a day to around 30 metres or more, with only a few minutes’ rest between them, over several hours. Some developed vertigo, nausea, paralysis or unconsciousness, and some died. The divers called it taravana, a word usually translated as something like “to fall crazily”.

Similar problems have been reported among other traditional breath-hold divers and, more recently, among spearfishers and deep competitive freedivers. In breath-hold divers, DCS seems to affect the brain more often than the joints, which is why the symptoms can look like a stroke.

Who is at risk today?

• Spearfishers. Long sessions, many dives, short rests and attention on the fish rather than the clock. Our post on spearfishing and freediving covers the safety side of hunting.
• Deep training days. Repeated dives beyond roughly 30 metres in one session.
• Very deep freedivers. DCS symptoms have been reported after only a few dives to extreme depth.
• Anyone mixing scuba and freediving on the same day.
• Beginners at moderate depths with sensible rests, for whom the risk is very low. A course session to 10 or 15 metres with plenty of time at the buoy is not the pattern that causes taravana.

Symptoms of decompression sickness in freedivers

Symptoms usually appear within minutes to a few hours after diving. They are easy to blame on heat, tiredness, seasickness or a migraine, so take them seriously:

• dizziness or vertigo
• nausea or vomiting
• numbness, tingling or weakness, especially on one side of the body
• blurred or patchy vision
• slurred speech, confusion or unusual behaviour
• severe tiredness
• an unusual headache
• joint pain, or an itchy, blotchy rash

If something feels neurologically wrong after a session of deep, repeated dives, treat it as possible DCS until a doctor says otherwise.

What to do if you suspect DCS

1. Stop diving and get out of the water. Don’t go back under to try to “push it out”; in-water recompression is not something freedivers should attempt.
2. Lie down and rest somewhere cool and shaded, with someone staying with you.
3. Give first aid oxygen at the highest concentration available, if there’s a kit and someone trained to use it. This is standard first aid for diving injuries.
4. Call for medical help and your dive insurer’s emergency line, and say clearly that it’s a diving injury.
5. Offer water to drink only if the person is fully conscious and can swallow safely.
6. Don’t fly or drive up to altitude. Treatment often involves recompression in a hyperbaric chamber, and lower pressure can make things worse. Our post on freediving and flying covers flight timing for healthy divers too.

Before a trip to the islands or a remote coast, find out where the nearest hyperbaric chamber is and how you would get there. From some dive spots it may be a flight away.

Safety: Numbness, weakness, confusion, or problems with vision or speech after diving need emergency medical attention. Don’t wait to see whether they pass.

Surface interval rules of thumb

No formula makes repeated deep diving risk-free, and agencies and coaches use different rules. These are some common ones:

Rule of thumb	Example	Typically used for
Rest at least twice your dive time	1 min 30 s dive: rest at least 3 minutes	Shallow and moderate dives
Depth in metres divided by 5, in minutes	30-metre dive: rest at least 6 minutes	Some coaches use it for deeper dives
Fewer dives and longer rests as depth increases	A handful of dives near your maximum, then stop	Deep training days

When two rules disagree, use whichever gives the longer rest. Keep the number of dives near your maximum depth small, take a long break after a deep session, and don’t stack several deep sessions into one day. A freediving watch with a surface interval display takes the guesswork out, and noting your rests in a freediving log shows whether you actually stick to them.

Scuba and freediving on the same day

Plenty of Indian divers hold both certifications, and island trips make it tempting to scuba in the morning and freedive in the afternoon. That’s the order to avoid. After scuba, your tissues hold far more nitrogen than after any freediving session, and the repeated descents and quick ascents of freediving on top of that load may raise the chance of bubbles forming.

The usual advice is not to freedive after scuba diving on the same day. The conservative option is to leave a full 24 hours between your last scuba dive and any deep freediving. Freediving first and scuba later is generally considered lower risk, but keep the freediving relaxed and moderate, and check with your instructor. Our comparison of freediving vs scuba diving looks at how the two fit together more broadly.

Planning a safe training day on your next trip

On a depth trip, plan one deep session a day and open it with progressively deeper warm-up dives. Time every surface interval, and drink water between dives in the heat. End the session when the plan says so, even if you feel good. If you feel strange afterwards, tell your buddy and instructor straight away, even if it seems minor or embarrassing.

Surface intervals, session planning and dive physiology are all topics you can study well before the trip. The freediving.in community for Indian freedivers is coming soon, so stay tuned.