TYBEE ISLAND, Ga. Oct. 3, 2004 — Below the deck of his shrimp boat, W.G. Smith recounts the story of his big catch more than 40 years ago. It was 1959 or 1960, as best Smith remembers, as he trawled for shrimp off the coast of Georgia. His net snagged on something large, an object so heavy he had to get a diving buddy to shake the net loose."He dived down and when he came up he said, 'That's a bomb,'" recalled Smith, 72. "I really didn't think much of it. I thought he was cutting the fool or something."Smith's...