As water does transport electricity quite good, it is highly doubtable that the use of any electricity devices for electroshocks will work in the way we are used to in air surroundings. There might be three different anwers... (a) highly targeted electroshocks to the surface, of e.g. a shark might work if the device is designed for underwater circumstances; (b) there is not really any effect as the electricity is distributed through the water and disperted; (c) in certain circumstances it might get dangerours (compare lightning to water)...