Two types of underwater pulsed discharge, spark discharge and corona discharge, have been studied in this paper. The pulsed corona discharge current under voltages ranging from 2 to 4 kV and conductivities of liquid ranging from 325 μS/cm to 20 mS/cm have been measured and the process of bubble's growth has been observed. Several results could be summarized from our experiments: (a) there is no conducting plasma channel in the underwater corona discharge; (b) effect of corona discharge does not depend on the distance of the gap between both electrodes; (c) discharge currents in corona discharge are highly dependent on conductivity which may prompt the fact that ionic current play a major role in the discharge process; (d) the underwater pulsed corona discharge can generate acoustical pulses when the conductivity is high enough. The corona acoustic intensity is similar to that of spark under the same conditions. A new model was put forward based on these experimental results.