The Florida Keys, the world's third largest barrier reef, are home to some 6,000 species of marine life. "That's more than you find in the Amazon," says Bob Holston, owner of Dive Key West. That might be stretching the truth, but at a site like the Haystacks, an easy 35-foot dive named for its 15-foot mounds of star coral, it's impossible to keep count. Clouds of outrageously colorful tropical fish, from tastelessly neon gobies to wrasses that look like they got trounced in a paintball fight, obscure the corals. At other sites, like the wreck of the Vandenburg, a 520-foot-long World War II transport boat, you might spot some of the sea's bigger wildlife – dolphins, sea turtles, and reef sharks – but Holston maintains that the Haystacks are the best thing going. You just can't beat all that local color.

More information: Two-tank dives cost $95 per person. PADI or NAUI certification required.