Answer: High water pressure increases the speed of sound.
Step-by-step explanation:
A hydrophone is a device that converts vibrations of sound waves, which are present in the form of pressure into water (or any liquid), into electrical energy. This means hydrophones work analogously to microphones in the air, so they are also known as "submarine microphones".
However, the speed of propagation of sound in water will vary according to its pressure, temperature and salinity. In the specific case of the pressure, when it increases, the speed of the sound waves also increases.
Also, as the pressure in the water is a function of the depth, in waters like those of the sea, the speed of the sound will increase with the depth.
Therefore:
High water pressure increases the speed of sound.