Abstract: A method to estimate source direction, range, and depth is proposed based on the data measured by ocean bottom seismometers (OBSs). Firstly, source direction is estimated separately using the vector sound field data obtained by two OBSs. Then, the source location is determined by the intersection point of the two directions, and the direction and range of the source can be obtained. Finally, source depth is estimated by the energy ratios of different modes decomposed from the signals obtained by one OBS. Based on the properties of modal functions in a shallow water environment with a negative thermocline, the depth of a shallow source can be obtained by the energy ratios of the higher-order modes, excluding the first-order mode, and the depth of a deep source can be obtained by the energy ratios of the higher-order modes to the first-order mode. Therefore, the depth of sources located at different depths can be estimated efficiently. The analysis of the OBS-measured signals is shown that the estimated source position is close to its actual position. The distance errors of the source from the farther and nearer OBSs are 1.5% and 14.1%, respectively. The estimated source depth is in agreement with the air-gun depth deployed in the experiment.