When should you perform a safety stop during a dive?

Performing a safety stop at a depth of 15-20 feet for three minutes after ascending from a deeper dive is an essential safety practice in scuba diving. This stop allows divers to off-gas nitrogen that has been absorbed into their bodies during the dive. As a diver ascends, the pressure decreases, which can lead to the formation of nitrogen bubbles if the diver ascends too quickly. The safety stop helps mitigate the risk of decompression sickness, commonly known as "the bends."

This practice provides a controlled environment for divers to allow excess nitrogen to safely release from their systems before returning to the surface. It is a recommended procedure, especially after deeper dives or when diving multiple times in a day, to enhance overall safety and reduce the incidence of related diving injuries.

The other options do not reflect the established practices for safety stops in scuba diving. For instance, performing a safety stop at any depth with the aim of preventing nausea does not address the specific physiological needs related to nitrogen off-gassing. Similarly, only feeling unwell or limiting the safety stop to night dives fails to consider that safety stops are relevant regardless of dive conditions or a diver's comfort level.