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Freediving and scuba diving are both exhilarating activities that allow people to explore the underwater world with different perspectives. While freedivers enjoy bubbleless immersions, scuba divers get to extend their bottom times while breathing compressed gas. Both activities require adequate training and the two of them are extremely rewarding.


However, combining these two activities without proper considerations can pose significant risks to divers. Freediving immediately after scuba diving can increase the risk of dangerous conditions such as decompression sickness (DCS) or shallow water blackouts. In this article, we will delve into the reasons why it is crucial to avoid freediving after scuba diving, emphasizing the potential dangers and the importance of adhering to the recommended safety guidelines.

Freediving and decompression sickness (DCS)

Freediving after scuba diving can lead to decompression sickness. When divers breathe compressed gas while scuba diving, the body absorbs nitrogen (N2) from the gas they breath. The nitrogen dissolves into the tissues, including muscles, organs, and other tissues, as the diver is subjected to increased pressure at depth.


During their ascent scuba divers need to allow sufficient time for the excess nitrogen to be slowly released until it is totally eliminated. As explained in Scubafacts article “Working out and scuba diving. All scuba divers need to know to stay fit and safe underwater”, this process is called off gassing; it starts as we ascend, it is enhanced by performing a safety stop and continues after surfacing. Proper off gassing ensures that the nitrogen is released gradually and safely, it prevents N2 coming out of solution, from forming bubbles.

Why does freediving can cause DCS if the diver is performing a breath hold dive?

Freediving does not directly expose a diver to DCS. The reason for this is simple: during a freedive, divers are holding their last breath taken on the surface. During the dive there is no breathing under increased pressure. As there is no gas exchange underwater, the nitrogen absorbed is only the one caught on the last breath before the descent. This amount is very small to produce DCS.


On the other hand, if a diver proceeds to freedive immediately after scuba diving without giving enough time for proper off-gassing, due to the rapid pressure change experienced -descending and ascending-, the excess nitrogen remaining in the tissues can come out of solution forming bubbles. The severity of DCS episode will depend on factors such as the amount of excess nitrogen still accumulated, the rate and depth of the freedive, and the individual's susceptibility.

Increased risk of nitrogen narcosis

Even though nitrogen narcosis is still not fully understood, it is known to be a condition experienced by scuba and freedivers at greater depths. It is believed that the increased partial pressure of nitrogen in the bloodstream is what impairs the cognitive functions, alters judgment, and can cause a sense of euphoria. Combining freediving with residual nitrogen from scuba diving further increases the risk of nitrogen narcosis particularly during deeper freedives. This can potentially lead to poor decision-making, loss of consciousness, or even drowning.

Reduced Oxygen Availability

The accumulated nitrogen from scuba diving can also affect the body's ability to transport and utilize oxygen efficiently. Engaging in

freediving immediately after scuba diving without allowing for sufficient off gassing time deprives the body of the opportunity to replenish the oxygen stores used during the scuba dive. This oxygen depletion can increase the risk of shallow water blackout, a potentially fatal condition where a diver loses consciousness due to low oxygen levels (hypoxia) near the end of the freedive. The combination between reduced oxygen availability and the physical demands of freediving can significantly heighten this risk.

Recommended course to follow

To mitigate the risks of freediving after scuba diving, divers should allow for adequate surface intervals. These intervals will provide time for nitrogen off gassing, and also allow oxygen replenishment. Many scuba and freedivers apply the same rules used for flying after diving to freediving after scuba diving. Allow for a 12 hours surface interval if freediving after a single scuba dive or, 18 hours if freediving after multiple scuba dives.


Following proper safety protocols, receiving appropriate training, and consulting with dive professionals can help ensure that divers engage in scuba and freediving activities safely. STAY DRY LONG ENOUGH AND ENJOY YOUR DIVES!

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