In today's world of unmanned underwater vehicles, the bottlenose dolphin is still the Navy's best defense against dangerous underwater mines. The dolphins have a unique ability to find objects using their biological sonar, called echolocation. They produce clicks - and then listen for the echos as the sound bounces off objects. They can then figure out if the object is a fish or a ship or a mine. Scientists at the Navy's Marine Mammal Program in San Diego, California have developed a "biosonar monitoring tool" so they can study just how echolocation works. One day they would like to build a robot that can do the same thing. Until then, dolphins will be guarding the coastline.