Bonito

Bonito needs 3 days: snorkeling down the Rio da Prata or Rio Sucuri, rivers so clear they look like natural aquariums, over a couple of days, and descending into the Gruta do Lago Azul, a cave with an intensely blue underground lake, on the other. April-September brings the best water visibility. It's mid-to-upper priced, with activities booked through limited daily slots. It's considered Brazil's ecotourism capital, with a model of mandatory guided visits and strict daily caps per attraction implemented since the 1990s to protect its spring-fed rivers.