http://www.pbs.org/wgbh/pages/frontl.../navycron.html
The Navy's Marine Mammal Program began in 1960 with two goals. First, the Navy wanted to study the underwater sonar capabilities of dolphins and beluga whales to learn how to design more efficient methods of detecting objects underwater, and to improve the speed of their boats and submarines by researching how dolphins are able to swim so fast and dive so deep. In addition to this research component, the Navy also trained dolphins, beluga whales, sea lions and other marine mammals to perform various underwater tasks, including delivering equipment to divers underwater, locating and retrieving lost objects, guarding boats and submarines, and doing underwater surveillance using a camera held in their mouths