Meet the Buddy-Watcher: a wearable device that lets divers stay in touch with their team underwater. It is a communication system based on ultrasound that generates vibration on the arm of your team member to get his/her attention. It works from a distance of up to 20 meters.
Buddy-Watcher’s vibration is noticeable through wet or dry suits. It works in fresh and salt water up to 40m deep.