I. Introduction
Recreational scuba divers, who dive in buddy pairs for improved safety, generally exchange information through hand gestures [1] that can include signals for boat direction, general well-being, air supply, interesting or hazardous marine life, swimming direction, and dive planning. For gesture-based communication to work well, several criteria must be met: a clear line of sight, attention of both divers, and a good understanding of the dive plan. Communication can be compromised when gesture sighting is inhibited, such as in murky water, with environmental obstacles, or simply loss of buddy attention. The above-mentioned factors often lead to the complete breakdown of the buddy system through diver separation that can, on its own, substantially increase the likelihood of an emergency.