AQUATEC Diving Duo-Alert Air Powered Surface & Underwater Signaling Device Scuba Dive BC BCD Gear Aquatec Duo-Alert Air Powered Surface & UnderWater (U/W) Signaling Device Signal in U/W and Surface, Volume:Approx. U/W:115-125dB Surface: 125~130dB It's very loud keep away from your ears. After each dive, the device should be pressurized, and activated in order to blow the trapped water out of unit. Always rinse with fresh water after use. Three models are available to fit over 95% of the inflators currently on th marketplace