A wonderful way to explore Arraial do Cabo [1]’s marine splendors is by boat. Frôr Turismo (Rua Santa Cruz 7, Loja 4, Praia dos Anjos, tel. 22/7834-0340, www.fror.com.br [2]) offers four-hour excursions for R$30, with stops in the Prainhas do Atalaia and Ilha do Farol.
On the island, aside from lounging on Praia do Farol [3], you can visit Gruta Azul, an underwater cavern that turns blue when illuminated by the sun.
Links:
[1] http://www.moon.com/destinations/brazil/rio-de-janeiro/costa-do-sol/arraial-do-cabo
[2] http://www.fror.com.br
[3] http://www.moon.com/destinations/brazil/rio-de-janeiro/costa-do-sol/arraial-do-cabo/beaches