Back and forth, back and forth: It was almost as if the great white shark was pacing, swimming the same small circle over and over. "Territorial loops," said Matt Lundberg, a fisherman who has cashed in as an aquatic tour guide ever since the 14-foot creature showed up in shallow water here last week. The 1,700-pound female--her gender identified by her dorsal fin--swam into an estuary off Naushon Island, about 3 miles from this Cape Cod village. Marine scientists believe she drifted too close to shore and became stuck in the 20-foot-deep lagoon. The area is rich in striped bass,...