The Aquatec Sub-Alert is not only starting to be a major requirement for many dive-aboard and dive operations, it is also an essential piece of gear that will add to the enjoyment of the dive to any buddy team that need to get each others attention underwater. Features: Horn works both UNDERWATER and on the SURFACE Volume: Underwater 115 to 125 dB Above water range approx. 0.5 to 1.0 mile