British navy used a hydrophone while searching for enemy submarines according to the Kriegsnachrichten of the Chef des Admiralstabes der Marine dated Berlin 23 August 1917

On board of the British drifter Thrive hired by the British Royal Navy at the Oranto Barrage, A rating is to lowering the hydrophone in the water, other crew members are standing by with earphones on. British Imperial War Museum

An item reported that a taken prisoner British naval engineer just the motor boats were fitted out with a hydrophone used when searching for submerged submarines. The hydrophone was made of 3 discs each with a diameter of a foot. When used stopped the motorboat and could identify what kind of propulsion the submarine was using that moment, thumping sound for diesel engines and humming sound for electric propulsion.

Note

1. The Three-Disc C-tube hydrophone like the Shark and Diamond configurations, is a portable passive-living system which was indeed used on board of small and fast vessels like coastal motor boats (CMBs). In 1912 was started with using hydrophones but the performance until mid-1917 was not more as to be called poor. Since then were more effective versions available.

Source

Bundesarchiv RM-40-622