Bahía Aventuras has run boats out of Uvita since 2007 and is wholly Costa Rican–owned, with the widest range on this stretch of coast: Marino Ballena for the humpbacks, Caño Island for snorkelling and diving, and the long day down to Corcovado at San Pedrillo.
The Caño Island trip is the one worth the money — the visibility is better than anywhere on the mainland coast, and the crossing usually turns up dolphins.