Virtually all Costa Rica beaches are backed by jungly forest, with slender coconut palms tilting over the shore, so that you can sunbathe in view of sloths and monkeys; it is not unusual to discover jaguar prints in the sand. Miles-long and dramatically scenic, the nation’s beaches are an integral part of the nature experience, made more so by the sheer number that serve as nesting sites for marine turtles.
Tortuguero National Park:  Stretching into the hazy horizon, this silvery beach backed by lush rainforest is the most important nesting site in the Caribbean for the green turtle, while monkeys, sloths, and other creatures can be seen in the treetops.
Cahuita National Park:  With several beautiful golden-sand beaches broken by rocky headlands, Cahuita is a great place to sunbathe or snorkel amid the offshore coral reef, while monkeys, coatimundis, and other critters abound in the rainforest shading the beaches.
Gandoca-Manzanillo National Wildlife Refuge:  Mirroring Cahuita, but more remote and with silvery sands, Gandoca-Manzanillo is an important nesting site for four species of marine turtles.
Playa Naranjo:  Surrounded on two sides by swampy estuaries good for spotting crocodiles, this lovely golden sand beaches provides access to trails that wind through Santa Rosa National Park . Big cats, tamanduas, and scarlet macaws are among the creatures to be seen.
Playa Grande:  Although leatherback turtles (and Ridley and green turtles in lesser numbers) are the main draw, Playa Grande is also good for spotting monkeys, coatimundis, and even deer and crocodiles in the adjacent Tamarindo National Wildlife Refuge , behind the shore.
Playa Ostional:  Time your visit for an arribada (mass arrival) of olive Ridley turtles and you’ll be rewarded with the unique sight of thousands of turtles crawling ashore to lay their eggs.
Montezuma:  Backed by tropical moist forest, this gorgeous miles-long beach offers serendipitous delights, such as possible sightings of monkeys, sloths, parrots, and toucans.
Manuel Antonio: The loveliest of Manuel Antonio National Park’s  four beaches, this scimitar of gold sands shelves into sheltered warm waters with a coral reef. Monkeys, iguanas, sloths, and even snakes are easily seen in the narrow strip of forest separating the beach from Playa Espadilla.
Barú National Wildlife Refuge:  Fronting varied habitats ranging from mangrove swamp to tropical moist forest, the beach is good for birding (from anhingas to roseate spoonbills) and animal sightings (from white-faced monkeys to tamanduas), and turtle viewing by night.
Playa Ballena: Although there’s plenty of wildlife in the coastal forests, the real treat lies offshore, in the Whale Marine National Park , where humpback whales gather to spawn their young. Boobies and frigate birds nest on the isle close to shore, and marine turtles come ashore to lay their eggs.
Playa Platanares: A short distance east of Puerto Jiménez , Platanares abuts both rainforest and mangrove, is an important nesting site for marine turtles, and offers the potential of viewing whales and dolphins offshore.
Corcovado National Park:  A coastal trail follows the three principal beaches lining the park, Playas Madrigal, Sirena, and Llorona. The 38-kilometer trail is sure to deliver an entire encyclopedia of animals and birds, including poison-dart frogs, four species of monkeys, and with luck even big cats.
Playa San Josecito: Within Piedras Blancas National Park  and accessible solely by boat, this dark-brown-sand beach is shaded by towering rainforest that is a tropical menagerie full of creatures from jaguars to scarlet macaws.
Playa Cativo: Also within Piedras Blancas National Park  and similar to nearby Playa San Josecito, Cativo is the setting of the Osa Wildlife Sanctuary where by prior arrangement you can handle spider monkeys, howler monkeys, and tamanduas.