What should divers do if they experience dizziness and lightheadedness underwater?

When divers experience dizziness and lightheadedness underwater, the safest and most appropriate action is to ascend slowly and safely. These symptoms can indicate a potential problem such as decompression sickness, nitrogen narcosis, or hypoxia; therefore, remaining at the same depth poses a risk of worsening the condition.

Ascending allows the diver to move to a shallower depth where pressure changes may alleviate symptoms and increase safety. A slow ascent is crucial to avoid introducing additional risks, such as decompression sickness that could occur from a rapid ascent.

The importance of communicating with a dive buddy is also emphasized, but the immediate focus should be on ensuring the diver's safety through proper ascent procedures rather than continuing the dive or remaining still, which could exacerbate the situation.