
If you go to Abrolhos on the mating season (July to November) you cannot miss a "Whale Watch" excursion. You would probably come across them on your way to Abrolhos, but it may be more interesting to go for the whale watch tour.
Before you can get to Abrolhos, you must first fo to Caravelas. Here you will find a number of tour operators authorized by IBAMA to sail to the archipelago. The cost per person for a day-trip is around R$220 (about USD 140). Check the page for Caravelas for instructions on how to get to Caravelas.
Once in Caravelas, you can only get to Abrolhos by boat. Your choices are: