For a truly unique and memorable experience, couples should consider holding their nuptials in the Florida Keys National Marine Sanctuary's warm, clear water, surrounded by colorful corals, softly waving sponges and rainbows of reef fish. In the Keys, it's easy. Many dive shops have been arranging underwater weddings for years. They can work with scuba-certified brides and grooms, prepare non-divers in the wedding party for the experience, even help mom and dad enjoy their first undersea excursion. A word of warning, though: it's nearly impossible to wipe away tears while wearing a dive mask, and handkerchief's are of no use under water. And unions of the deep are perfectly legal.