When should divers signal for an ascent during a cavern dive?

Signaling for an ascent during a cavern dive is critical for divers' safety and is primarily determined by the status of the diver’s air supply or the maximum dive limits being reached. When air supply is low, it directly indicates that the diver may not have sufficient gas remaining to safely complete the ascent and any necessary safety stops. This is a fundamental principle of diving, as maintaining adequate air supply is essential for a safe return to the surface.

Additionally, reaching the predetermined limits of the dive provides a necessary check to ensure divers do not exceed their planned depth or time, which could increase the risk of decompression sickness or other hazards. Responsible diving practices emphasize the importance of adhering to these guidelines to ensure safe ascents.

When considering other options, while factors like sudden changes in water temperature, poor visibility, or maximum depth can indicate the need for caution and may influence the decision to ascend, they are not as immediate or critical as the state of the air supply or adherence to dive limits when it comes to signaling for an ascent. Thus, prioritizing air supply and limits directly aligns with maintaining safety during cavern dives.