Decompression accident during freediving: understand the risks of diving and protect yourself effectively

In freediving, a decompression accident (DCS) represents a real risk for both amateur and professional divers if certain precautions are neglected. Contrary to popular belief, freedivers can suffer from decompression accidents during repeated and deep dives. The principle? Nitrogen, dissolved in the tissues, forms bubbles that become dangerous during ascent.

In this article, Europ Assistance explains the mechanisms behind decompression accidents in the context of diving. With this understanding, you’ll be able to adopt good practices and venture into the ocean depths with greater peace of mind.

How does a decompression accident occur in freediving?

Why can freedivers suffer from decompression accidents?

At first glance, the idea may seem surprising! How could a freediver suffer a decompression accident when they don’t breathe underwater? The key lies in pressure—and how our body handles gases.

Underwater, pressure increases very quickly: at 10 meters, it doubles compared to the surface. At 20 meters, it triples.

This pressure compresses the air in the lungs and promotes the dissolution of nitrogen contained in it. A single descent is generally not a problem: upon returning to the surface, the body naturally eliminates this nitrogen.

But during intensive sessions (dozens of deep dives in a day, such as in spearfishing or intense training), the body doesn’t always have time to eliminate all the nitrogen between dives. Gradually, small amounts can accumulate in the tissues, leading to a risk of decompression accident in freediving.

What happens when you ascend too quickly?

During ascent, pressure gradually decreases. If the tissues have accumulated nitrogen after many dives, a rapid ascent can cause this nitrogen to form bubbles—just like when you open a soda bottle too quickly.

These microbubbles can disrupt blood circulation, irritate certain tissues, and cause symptoms of decompression sickness: joint pain, neurological disorders, extreme fatigue, numbness, dizziness…

This phenomenon remains rare in freediving, but it can occur:

• after many deep dives;
• with recovery times that are too short;
• during long and intense sessions.

To reduce this risk, experienced freedivers ascend calmly, breathe normally at the surface, and space out their dives. We don’t talk about “decompression stops” as in scuba diving, but rather a progressive ascent combined with sufficiently long recovery times between dives.

What situations cause decompression accidents?

Under what conditions do accidents really occur?

If you dive recreationally, a few descents to 10–15 meters usually won’t cause harm. Decompression accidents in freediving mainly affect intensive practitioners who dive repeatedly and at great depths.

The most at-risk profiles are competitive spearfishers or freedivers undergoing intense training. They may perform 10 to 15 dives per hour, for 4 to 8 hours straight, often at depths greater than 30 meters.

What situations increase the risk of DCS?

• Performing too many dives too quickly. If you allow only 1 or 2 minutes between each descent, your body doesn’t have time to eliminate nitrogen;
• Repeated deep dives. Beyond 20–30 meters, nitrogen dissolves much more in the blood, increasing the risk of decompression accidents;
• Using an underwater scooter. This device allows you to descend and ascend very quickly without effort, enabling more dives—and more risk of DCS;
• Ascending too quickly. Decompression stops in freediving help reduce the risk of accidents. The faster you ascend, the more violently bubbles form.

What are the symptoms of a decompression accident after diving?

Recognizing the first warning signs

The danger of a decompression accident in freediving is that it doesn’t always strike immediately. While half of the symptoms appear within 10 minutes after diving, and 75% within the hour, 25% of DCS cases only manifest within 24 hours after surfacing. You may feel fine when exiting the water, then develop symptoms later.

Among the first warning signs that should never be ignored:

• Overwhelming fatigue that exceeds normal post-effort tiredness
• Persistent nausea, sometimes with vomiting
• Dizziness, lightheadedness, imbalance, or the sensation that everything is spinning
• A stubborn headache that doesn’t go away with usual medication
• Neurological issues (numbness, tingling, weakness, confusion, unusual anxiety or behavioral changes)

If you experience one or more of these symptoms after an intensive freediving session, don’t take them lightly. They may be the early signs of a decompression accident.

When it gets serious

Decompression accidents can affect the brain or spinal cord. This happens when small gas bubbles disrupt circulation and nerves. Without treatment, the consequences can be severe.

Here are some warning signs to watch for after an intense freediving session:

• Blurred or double vision
• Difficulty speaking
• Numbness or weakness in an arm, leg, or the face
• Clumsy movements, loss of coordination

These symptoms indicate a medical emergency. Even if you feel fine at first, don’t delay contacting a doctor or specialized center as soon as symptoms appear. Every minute counts.

How to prevent a decompression accident

The good news is that decompression accidents in freediving are easily preventable if you follow a few basic rules and use common sense.

• Respecting ascent and decompression stops

Even in freediving, some repeated and deep dives require a gradual ascent to allow nitrogen to dissipate. Follow your dive computer’s instructions, or plan your ascents according to official safety recommendations.

• Using a dive computer

A computer calculates your nitrogen saturation, the necessary recovery time, and guides you to stay within safety limits.

• Respecting recovery times between dives

The deeper or longer the dive, the more nitrogen accumulates and needs to be eliminated. Wait the recommended time before diving again, rather than taking unnecessary risks.

• Limiting the number of dives

Too many closely spaced dives increase the risk of DCS, even if you take proper breaks.

• Hydration and physical condition

Drink before, during, and after diving. Also try to avoid fatigue, stress, or lack of sleep, which make the body more vulnerable

• Absolute prohibitions
  • No freediving after recent scuba diving (wait 12–24 hours)
  • No scuba diving after intense freediving (wait 12–24 hours)
  • No flying within 12–24 hours after a deep session
  • No intense physical effort after diving
  • No alcohol before or after diving

What to do in case of a decompression accident?

Follow an emergency protocol

Upon exiting the water, if you or someone nearby doesn’t feel well, don’t waste a second. Here’s a simple and effective emergency protocol:

• Remove the person from the water immediately and ensure their safety
• Call emergency services (in Switzerland: 144), and specify that it is likely a decompression accident following freediving
• Lay the person flat (not seated)
• Administer pure oxygen if available (mask or tank), to help reduce bubbles and reoxygenate tissues
• Protect them from the cold with a blanket or dry clothing
• Hydrate them if they are conscious and able to drink
• Note the exact time symptoms appeared and details of the dives: number, depth, duration

Every minute gained increases the chances of full recovery. Do not underestimate the symptoms—call for help.

The hyperbaric chamber: the essential treatment for DCS

Decompression sickness (DCS) in freediving cannot be treated with medication or simple rest. The only scientifically recognized treatment is hyperbaric therapy.

The principle is simple: in a hyperbaric chamber, pressure is gradually increased, simulating the effects of a slow ascent. At the same time, the patient breathes pure oxygen. This combination helps to:

• Reduce the size of nitrogen bubbles that block blood flow and affect tissues
• Reoxygenate tissues deprived of normal circulation
• Eliminate excess nitrogen in a gradual and controlled manner

Sessions can last several hours. In the most severe cases, multiple sessions over several days may be necessary to optimize recovery.

Speed is a determining factor

Rapid intervention is crucial to limit long-term damage. Ideally, the person should be treated within 6 hours of symptom onset to maximize the chances of full recovery. After 24 hours, some neurological or vascular damage may become permanent, making swift action essential.

Think about your travel insurance!

An accident during a holiday activity can quickly become expensive. Emergency medical transport (sometimes by helicopter), hospitalization, recovery costs... These can amount to tens of thousands of Swiss francs.

The good news is that Europ Assistance travel insurance covers activities during your trips, including diving (as an amateur and at reasonable depths). Specifically, you benefit from the following coverage:

• In case of cancellation, if you’ve already paid and booked the activity
• Repatriation and emergency transport
• Medical expenses (Comfort option)
• 24/7 assistance

→ Calculate your premium for free

Frequently asked questions about decompression accidents related to freediving

Why is DCS called “the bends”?

DCS is called “the bends” because it was first discovered among divers and workers exposed to high pressure in hyperbaric chambers in the early 20th century. The term comes from the enclosed installations used to control pressure, employed in deep diving and underwater work.

Can freedivers suffer decompression accidents?

Yes! Although rare, decompression accidents related to freediving do exist and have been documented in medical literature, notably in the work of Dr. Nicolas Héran in the 1990s. It mainly affects freedivers who perform repeated deep dives during intensive training or spearfishing.

How much recovery time is needed at the surface?

In freediving, there are no official decompression tables. However, surface recovery must be sufficient to allow the body to eliminate accumulated nitrogen. The deeper or longer the dive, the longer the surface rest should be. It is recommended to avoid series of deep dives without extended breaks.

Can freediving and scuba diving be combined?

It is strongly discouraged to practice freediving after scuba diving. Descending while freediving can recompress residual nitrogen microbubbles, increasing the risk of decompression accidents. Standard recommendations suggest waiting 12 to 24 hours before freediving after scuba diving.

What warning signs should raise concern?

Symptoms of a decompression accident usually appear within hours after a diving session. Possible signs include unusual fatigue, headaches, dizziness, nausea, anxiety, tingling, numbness, vision or speech disturbances, or muscle weakness. Any neurological symptom or abnormal sensation after an intense freediving session requires urgent medical attention.

How long should you wait before flying after diving?

It is recommended to wait 24 hours after a deep freediving session before flying. Cabin pressure drop can cause expansion of nitrogen microbubbles still present in the body, leading to a risk of decompression accident in the air.

Can a decompression accident leave permanent damage?

What is taravana?

Taravana is a Polynesian term derived from tara (to fall) and vana (crazy). It historically refers to decompression accidents observed among pearl divers in the Tuamotu Islands, French Polynesia. This syndrome was described in 1947 among divers who operated under extreme conditions—about 15 dives per hour for 6 consecutive hours, at depths of 20 to 45 meters, with very short recovery times. These accidents manifested through severe neurological symptoms including dizziness, nausea, and motor and sensory disorders.

Are beginners at risk of decompression accidents?

Beginners in freediving are generally not affected by decompression accident risks, as they lack the physical capacity to perform numerous deep dives—which is a good thing. This risk mainly concerns high-level freedivers, especially those involved in competitive spearfishing or intensive training over extended periods.

Does my insurance cover diving accidents?

Europ Assistance travel insurance covers underwater activities, including diving, as long as it is practiced as an amateur and at reasonable depths. Always check the specific terms of your policy before traveling.