The Great Dolphin Dilemma | Hakai Magazine
Military use of dolphins dates to the early 1970s, when the navy deployed the animals during the Vietnam War. The navy also realized they could train dolphins to detect what the military perceived as threats, and they taught the animals to find underwater mines and spot foreign objects in the water, such as remotely operated spy vehicles and enemy divers. Their ongoing research with the navy includes studying the impacts of anthropogenic noise on the echolocation and hearing of navy dolphins (and sea lions, another military sea mammal), which informs efforts to reduce negative impacts on wild marine mammals.
Source: www.hakaimagazine.com