Atlantis, a curious rock formation under about 20 feet of water, 500 yards offshore at Bimini Bay, is shaped like a backward letter J, some 600 feet long at the longest end. It's the shorter 300-foot extension that piques the interest of scientists and visitors. The precision patchwork of large, curved-edge stones form a perfect rectangle measuring about 30 feet across. A few of the stones are 16 feet square. It's purported to be the "lost city" whose discovery was predicted by Edgar Cayce (1877-1945), a psychic with an interest in prehistoric civilizations. Archaeologists estimate the formation to be between 5,000 and 10,000 years old. Carvings in the rock appear to some scientists to resemble a network of highways. Skeptics have pooh-poohed the theory, conjecturing that they are merely turtle pens built considerably more recently.