The Amazon flows to the sea, but the Galapagos Islands are actually out in the sea and offer just as much opportunity for adventure and education (minus some meat-eating fish with a very bad reputation). Clustered around the equator off the coast of Ecuador, the Galapagos are famous for inspiring Darwin's theory of evolution. The Galapagos have plant and animal species not seen anywhere else in the world, including a bird called the Blue-footed Booby. We'll pause to let you snicker like a 13-year-old boy.
Galapagos cruises are usually on smaller boats to minimize environmental impact, and feature educational lectures and hikes. Many also offer snorkeling and SCUBA diving, so you can get up close with all of the environments around the Galapagos. For even more adventure, you can charter your own sailboat in Ecuador and sail it to the Galapagos yourself (this assumes, of course, that you know how to sail).