As dive site names go, Dirty Rock isn’t the most inviting, but this rocky outcropping about a half mile off the north shore of the island has one of the largest hammerhead shark populations in the world, along with giant manta rays. Expect 120-foot-plus visibility. For even more mantas, head to Dampier Head at the southwest corner of the island, where rays with wingspans up to 10 feet seem to like to swim with divers.
For a little legwork between dives, head up 2,092-foot Mount Yglesias, the highest peak on the island. The trail to the summit, one of several on the island, leads through rainforest (and passes the wreck of a B-24 in the jungle), and the view of the Pacific at the top might even make you forget about your swim fins for a while.
A natural laboratory similar in some ways to the Galapagos (which lacks the tropical rainforest here), Cocos is home to an estimated 60 endemic animal species. Bird watchers will note that the rocky islets off the island are prime nesting areas for seabirds, including the red-footed booby, and that three of the island’s 70 or so species include three found nowhere else: the Cocos Cuckoo, the Cocos Finch (shades of Darwin!), and the Cocos Flycatcher.