BEIJING, April 13 (Xinhuanet) -- Officials at the U.S. Navy's marine mammal training center in San Diego, Calif., opened its doors to the media Thursday to demonstrate why 30 dolphins and sea lions will be used to patrol against terrorists in the waters near Washington state's Naval Base Kitsap-Bangor, a home to nuclear submarines.

    The Navy says sea lions and dolphins constitute its best line of defense against underwater attacks.

    "Biologically, they are better than anything we have ever made," said Mike Rothe, head of science for the Navy's marine mammal program.

    Both species are trained to locate mines and swimmers in murky waters. Working together, the dolphins are trained to drop a flashing light by an underwater swimmer, while sea lions can attach a tether to an intruder.

    The dolphins live in a series of interconnected pens by several jetties in the harbor. Most enclosures are about 30 feet (9 meters) wide by about 30 feet (9 meters) long, with net floors about 10 feet (3 meters) down. By opening gates between the pens, handlers let the dolphins interact for much of the day, Rothe said.

    Animal rights activists are protesting the Navy's plans to send the dolphins and sea lions to Washington state. They worry that waters in the region, which are about 10 degrees Fahrenheit (6 degrees Celsius) cooler than in San Diego Harbor, could put stress on the animals. They also are concerned diseases could be transmitted to the area's native orca population.

    "There are no bottlenose dolphins in these waters for a reason and I would say it's because it's too darn cold," said Seattle-area marine biologist Toni Frohoff.

    The last time the marine mammals were deployed overseas was in the Iraqi harbor of Umm Qasr in 2003, where they located underwater mines and cleared a path for Marines to land. They also were used in San Diego in 1996 when they patrolled the bay during the Republican Party's national convention.

    (Agencies)