How long after a dive should one wait before making a repeat dive?

The recommended waiting period before making a repeat dive is 12 hours. This guideline is founded on the need to allow the body to off-gas nitrogen absorbed during the first dive. After a dive, especially when deeper or longer dives are involved, nitrogen builds up in the body’s tissues due to increased pressure. This nitrogen must be eliminated to reduce the risk of decompression sickness, also known as "the bends."

Waiting for 12 hours gives the body enough time to safely off-gas and lowers the likelihood of any residual nitrogen causing issues during subsequent dives. This precaution is especially important after multiple dives or dives exceeding certain depths, as the risk of decompression sickness increases with both the amount of nitrogen absorbed and the timing of the next dive.

In the context of other waiting periods, while some divers may choose longer intervals depending on the specifics of their dive profile, the 12-hour guideline is a widely accepted standard for ensuring safety when planning to dive again soon after a previous dive.