A pulse generator 310 for deterring marine animals, the pulse generator comprises a pressure pulse generation component (12 figure 6) and a control component 316 configured to control a first parameter relating to the pulses duration and a second variable parameter relating to the pulses peak amplitude. The length of the negative or positive part of the pressure pulse may be configured to correspond to or exceed an expected size of a marine animal. The pulse generation component may comprise a fluid reservoir 326 that discharges fluid through a nozzle 330 using a valve 328 to crate the pressure pulse. The pulse generation component may comprise a power supply (440 figure 4) that generates an arc between two electrodes (442, 444 figure 4) to create the pressure pulse. The pulse generation component may comprise a transducer (546 figure 5) that generates a signal and a diaphragm or speaker (548 figure 5) that is configured to create a pressure wave in response to the signal.
