Life on land offers plenty of tantalizing options for adventure travelers, but theres a whole other world of excitement waiting under the sea. You don't have to be a daredevil to take on these deep-sea adventures, but a visit to any one of these amazing spots will require some guts. While some of these destinations are perfect for snorkelers, others will require a bit more know-how in the water. Either way, the stunning scenery and abundance of underwater life are sure to make your dive or swim a memorable experience.