Meet Buddy-Watcher: a wearable device that uses ultrasound technology to keep you connected with your team underwater. Just wear it on your wrist like a watch and press its button to trigger a vibration on the arm of your friend. It is useful when you are in trouble or want your diving partner to check something out.
Buddy-Watcher is designed for fresh and salt water to 40m deep. It has a frequency of 64 kHz and does not cause any disturbance underwater. It lasts up to 8 hours.