Hydrophonic

Even the sophisticated sonar and hydrophonic devices which cover both the Atlantic and Pacific Oceans from shoreline to hundred of miles out to sea would be circumvented by this Trojan-Horse technique.

Although others may have been sunk earlier, the first submarine confirmed lost in consequence of hydrophonic detection was the German UC-49 on August 8, 1918.

Success for Operation Teardrop had come not from aircraft but from the tedious sonar and hydrophonic probing of the depths by surface ships.