A resonant tube having an inlet fitting at one end for connection to the regulator hose attached to an intermediate pressure port on the first stage of a scuba diver's regulator and containing therein a sound generator responsive to pressurized air for generating an audible sound to be propagated against the wall of such tube. The outlet from such tube includes a normally closed air valve which may be selectively depressed to release air from such resonator tube causing incoming air to flow through such generator to generate such audible sound. Frequencies generated are propagated to the surrounding water or air.
