A method for detecting the depth of a liquid body. A source of pressurized gas is engaged to a weighted sensor by means of a single elongated tube. The sensor is positioned at the bottom of the liquid body. A solenoid valve, which regulates the flow of gas in the tube, is periodically opened to provide a pulse of overpressure which exits the underside of the sensor in a pressure-equalizing stream of bubbles. After a brief, predetermined settling time, a reliable pressure/depth indication is obtained from a transducer in communication with the single tube.