Hydrophones originate in the speculative, but never built, underwater signalling systems first proposed by Lucien Blake (1889) , they were then followed by the fully realised water proof telephone systems developed by Elisha Grey (1901) . Falling out of use once more, interest in these died but they were brought back to life by deployments during both world wars as passive sonar listening and detection devices.
The first hydrophones, invented during World War I by British, American and French scientists, were used to locate submarines and icebergs. These were passive listening devices. The committee was named the ASDICS (for Anti-Submarine Detection Investigation Committee). R.W. Boyle In 1912 returned to Canada from the University of Manchester and took up the position of the first head of the department of physics at the University of Alberta where he began his ground-breaking research on ultrasonics. With the outbreak of World War I, Boyle joined the staff of Britain’s Board of Invention and Research, working for the Royal Navy at Parkeston Quay. In 1916 he was placed in charge of top secret research on ASDICS. The first known sinking of a submarine detected by hydrophone was the German U-Boat UC-3, in the Atlantic during World War I on April 23rd, 1916. 
  Beyer. R. T. “Sounds of Our Times: Two Hundred Years of Acoustics” (1999) Springer-Verlag New York.