Fernando de Noronha is a tropical archipelago around 200 miles off the northeast coast of Brazil, home to a national marine reserve with a vibrant underwater ecosystem. There are dozens of dive sites around the islands, suitable for both beginner and experienced divers. The conditions are perfect, with warm waters, pristine coral reefs, and excellent visibility, and the area is home to hundreds of species of fish, including sharks, rays, eels, and groupers; there are dolphins and sea turtles, too. (A hawksbill turtle conservation project is based here.) Atlantis Divers, Aguas Claras, and Noronha Divers are the local dive schools.
For something incredibly cool and unusual, try planasub, which is a kind of tripped out combination of waterskiing, sledding, and snorkeling that was apparently invented here in Fernando de Noronha. Basically, you strap on mask and snorkel and grab on to a plastic tray that is attached to a motorboat by a rope. The boat pulls you along and you coast along the surface, but can angle the tray down to dive beneath the water for as long as you can hold your breath. If you’re really lucky, you’ll encounter a pod of dolphins that love the game nearly as much as you do.