How long must someone wait after scuba diving before ascending to an altitude of 8,000'?

The correct answer indicates that the waiting time after scuba diving before ascending to an altitude of 8,000 feet can vary depending on the type of ascent. For recreational scuba diving, the general recommendation is to wait at least 12 hours after a single dive before flying or ascending to higher altitudes if the ascent is uncontrolled. This allows the body sufficient time to eliminate excess nitrogen, which can build up in the tissues during the dive.

In cases of multiple dives or if the divers are at greater depths, the guidelines suggest a longer wait time of up to 24 hours, particularly for controlled ascents where the potential to develop decompression sickness or "the bends" is higher. This distinction is important because the risks associated with a rapid ascent from pressure underwater can lead to serious medical complications if not appropriately managed.

Thus, indicating that both 12 hours and 24 hours are applicable depending on the circumstances—like dive profile and number of dives completed—accurately encompasses the best safety practices for divers wishing to ascend to altitude after diving.

Choices that suggest waiting immediately after surfacing or offer a singular timeframe do not consider the variations in diving conditions and physiological responses.