The Dive Alert Plus is a specially designed, small, light weight pneumatic signaling device that uses quick-connect/disconnect hose couplings to become an integrated part of your power inflator. Installation is easy and takes only a moment. It uses a small amount of air from your SCUBA tank to make a piercingly loud sound in air or water. People have been able to hear a DiveAlertPLUS one mile away from a diver in need above water. In conditions where visibility is limited, a DiveAlertPLUS can be a life saver. Underwater you can sound for attention quickly with a squeeze of the device. Please verify the model is compatible with your BCD (see description below)