Boat Tour in The Osa Peninsula Found: 2 | Change Filter Options Rio Sierpe Mangrove Tour Explore the Rio Sierpe mangroves in Costa Rica and discover its wildlife with Osa Rural Tours Cooperative. Dolphin and Whale Spotting on Golfo Dulce Explore the rich marine ecosystem of Golfo Dulce, home to dolphins, whales, and coral reefs perfect for snorkeling.