I advise you: this message only talks about military dolphin.
Everyone is familiar with a security patrol dogs, they are very effective on land but they have troubles on the sea. For this reason, dolphins are trained by military. In fact, marine mammals are so important to the Navy that there is an entire program dedicated to studying and training them. It is called the Navy Marine Mammal Program, and it starts in 1960.
Dolphins are trained to detect underwater mines and/or enemy swimmers. It is said that they have biological sonar, called echolocation, which makes them very effective at locating sea mines