KEYPORT, Wash. _ The Navy held an open house last night at the Naval Undersea Museum in Keyport to explain its plan to use dolphins and sea lions as underwater guards at the Trident submarine base at Bangor. Animal rights advocates say the Hood Canal water is too cold for the dolphins from San Diego. Demonstrators brought inflated dolphins and sea lions clad in camouflaged shirts. Some knitted clothes for the animals. The Navy is holding another public meeting on the idea this evening in Seattle (starting at 5 p-m at Holiday Inn, 211 Dexter Ave. N.) The Navy plans to us as many as 30 dolphins and sea lions to patrol around Bangor for suspicious swimmers and scuba divers. The animals already are being used to guard the Trident base at Kings Bay, Georgia. The animals are trained to deploy a flashing light or even to put a clamp on the leg of an intruder.