What is a common indication that a diver should ascend?

Experiencing discomfort or distress while diving is a critical indication that a diver should ascend. This discomfort could manifest as physical pain, difficulty in breathing, feelings of anxiety, or any other symptoms that suggest the diver's safety may be compromised. Diving involves various risks, including but not limited to changes in pressure, potential equipment malfunction, or health-related issues like decompression sickness. When a diver feels any form of distress, it is essential to prioritize safety and initiate an ascent to prevent further complications and ensure adequate monitoring by dive personnel.

In contrast, the other options do not indicate a need to ascend. A sudden increase in temperature is not typically a reason to change depth, as it can happen due to natural variations in the underwater environment and often does not pose an immediate risk. Feeling calm and relaxed suggests that the diver is in a stable condition and can continue the dive safely. Lastly, seeing underwater wildlife can be a normal and exciting experience during a dive and does not serve as an indication for ascent unless it is accompanied by other concerning factors.