Coming from someone who dives as well as sails, being stranded in the ocean is a definite concern, one of a diver’s worst fears. Just saw this the other day and thought it was a very neat device. A bit pricy, but it's very small, has built in strobes, GPS, DCS, VHF, waterproof on the surface, water proof shut to 425 feet, and can attach it to your PFD. Still new, so I don’t know anyone that has one, but I will be buying one before my next ocean dive. http://www.alertdiver.com/nautilus_lifeline