SOSUS hydrophones, laid on the seabed and connected by underwater cables, were used, beginning in the 1950s, by the U.S. Navy to track movement of Soviet submarines during the Cold War along a line from Greenland, Iceland and the United Kingdom known as the GIUK gap.
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Ernest Rutherford, in England, led pioneer research in hydrophones using piezoelectric devices, and his only patent was for a hydrophone device.