Blue Hole, Lighthouse Reef, Belize

With very little marine life, the Blue Hole is more a geological trip than a visit to the zoo. An unbelievable sight from the air, the almost perfectly circular Blue Hole was created by what was a dry cave system in the Ice Age. At 110 feet below sea level, the caves have stalactite formations where reef and hammerhead sharks lurk in the shadows. The water stands perfectly still and one can stare up through the passage to the sky above. "It's so distinctive a feature. It's very striking," says Morrisey. May and June are the best months to spot sharks circling the hole.

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