Which signal indicates "Attention" underwater?

The signal that indicates "Attention" underwater is when a diver moves their light slowly back and forth. This is a widely recognized communication method among divers to capture the attention of others in the immediate area, especially in environments where visibility may be limited or where verbal communication is impossible. By slowly scanning the beam of light, it conveys a clear message that something important requires others' attention.

This technique is particularly useful in cavern diving where acoustics can be challenging and the ambient conditions may hinder direct visual contact. It provides a non-intrusive way to alert fellow divers without causing alarm, allowing for effective communication in potentially hazardous situations.

Other options, while they may have their uses in different contexts, do not specifically denote the "Attention" signal in underwater scenarios.