John Pennekamp: Put Your Face in the Water

First undersea park in the US, Mile Marker 102.5. Seventy nautical square miles of Atlantic reef and the best snorkeling in the continental United States. The glass-bottom boat is fine if you're cautious. The snorkel trip is the real experience.

Thirty-minute boat ride out, water shifts from green to that impossible Keys blue, you roll off the side and the world above disappears. Brain coral the size of a Volkswagen. Parrotfish gnawing rock with beaks that sound like someone eating celery. Sea fans moving in the current. A nurse shark dozing under a ledge with zero interest in your existence. The colors are not exaggerated by postcards — they really are that vivid, and the first time an angelfish glides past a purple sea fan in a shaft of underwater light, something shifts permanently.

Book the morning tour — calmer water, better visibility. Use reef-safe sunscreen or you're literally killing what you came to see. Kayak trails through the mangroves too, if above-water is more your speed.