What is an additional indication that a diver may be below the water's surface?

Bubbles are indeed a clear indication that a diver is below the water's surface. When divers breathe underwater, the air they exhale forms bubbles as it rises to the surface. These bubbles are a visual cue to both other boaters and swimmers that there is a diver nearby. Being aware of such signs is crucial for safety, as it helps avoid potential accidents or collisions.

Other options, while they may indicate a diver's presence in the water, do not provide the same level of direct information. For example, a colorful buoy is often used to mark the location of a diver or snorkeling area, but does not explicitly show whether a diver is below the surface at that moment. Sound signals may be used by divers to communicate, but they are not a visual sign of a diver’s presence. A diver watch can track time or dive depth but does not directly signal a diver's location in the water. Thus, bubbles serve as the most immediate and recognizable indication that a diver is submerged.