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This double Scuba Alert air powered surface and underwater signaling Device consists of two horns. One horn for use at the surface, one horn for use under water. Connect the device between the inflator and the low pressure hose and it will produce a sound that will attrack attention. It is very loud so keep it away from your ears!
Volume at the surface: approximately 125-130 dB
Volume under water: approximately 115-125 dB