Hin Ta Hin Yai Rocks, Koh Samui, Thailand

Anyone for gulf?

Take a look at Thailand on a map and you'll see a narrow 'tail' of land separating the Gulf of Thailand from the Andaman Sea. The two bodies of water stand in sharp contrast: The deep, wild Andaman has a mean depth of more than 3,500 feet, while the warm, turquoise-tinted Gulf averages under 200. Just offshore from both coasts, hundreds of islands dot the seas: We're on the shores of Ko Samui (the nation's second-largest island after Phuket)—a touristy locale known for seaside granite formations and gorgeous waterfalls.