What must divers do prior to moving to a higher altitude after diving?

Before moving to a higher altitude after diving, divers are required to wait for a sufficient surface interval to avoid decompression sickness. This is crucial because when divers come up from a dive, they need to allow time for excess nitrogen absorbed in their tissues to be metabolized and safely eliminated from the body. If they ascend to a higher altitude too soon after diving, the reduced atmospheric pressure can cause nitrogen bubbles to form in the body, leading to decompression sickness, which can be serious and even life-threatening.

The amount of time needed for a surface interval depends on the depth and duration of the dive, as well as the type of diving conducted (such as single versus repetitive dives). Recognizing the importance of calculating this interval is vital for any diver's safety.

Other options do not promote safety in relation to altitude changes post-dive. Immediate ascent, safety stops, and resetting dive computers do not address the critical aspect of avoiding decompression illness that results from inadequate surface intervals.