I spent three weeks in Brazil this year and the highlight of my trip has to have been Bonito.  It is an eco tourism town located in the west of Brazil near Campo Grande.  We stayed in the youth hostel www.ajbonito.com.br and organised all the trips through them.  You have to snorkle down Rio de Prata and if your feeling a bit daring then the Abismo Anhuma is a thrilling 72 meter abseil down into a cave followed snorkelling or diving in clean water inside a cave. The food in the hostel is great value and really good homecooked Brazilian fare.