Our hands-down favorite for local diving is the Nautilus Lifeline. The Lifeline is fully waterproof and depth rated to 425 feet. It’s also falling-down-simple to use. The Lifeline makes use of VHF radio and GPS. Press the green button, and you can use your VHF radio to make nonemergency contact with the dive boat. The orange button, preset to Channel 16, sends out your verbal distress call directly to the Coast Guard, and the red but- ton transmits a digital Mayday with your exact coordinates to the Coast Guard and any boat in the area equipped with Digital Selective Calling.