The eastern shore of the Osa Peninsula is bordered by the deep-blue Golfo Dulce, where game fish lurk and some very long waves come to die. Sea kayaks are the best means of exploring the area. The upper gulf's serrated shoreline is a wilderness made for flatwater cruising, assuming of course that you have no particular phobia about crocodiles. And near the entrance, where the Golfo Dulce and the Pacific clash in the unruly manner so beloved by surfers and big-game fishermen, open-water paddlers will find just about all the excitement they can handle.
Bivouac on the gulf at Puerto Jimñez, a former gold-rush boomtown now filled with laid-back Americans who all seem to have headed south without leaving a forwarding address. Find themand information about local adventuringat Restaurante Carolina, where the cold beer starts flowing well before noon. Don't be concerned by the appearance of intrigue: If a woman leans over to whisper to you conspiratorially that she used to work for the government, she probably means only that she recently lost her job as a postal worker.
Escondido Trex, which has an office near the bar in the Carolina, runs single- and multiday kayak camping trips in the Golfo Dulce. Bring your snorkeling gear and hope for waters calm enough to allow you to shoot through the Matapalo Arch, a curving rock at the southern tip of the peninsula ($85 for an overnight trip, including all meals and gear; phone/fax 735-5210).
San José-based Ros Tropicales, Costa Rica's major paddle-sport operator, also offers a Golfo Dulce sea kayaking trip ($1,370 for nine days; 233-6455). North Carolina's Nantahala Outdoor Center began leading trips to the area two years ago; its ten-day tours mix sea kayaking and inland hiking ($1,475; 704-488-2175).
Not far south of Puerto Jimñez, the Osa Peninsula comes to an end. If you've come this far, treat yourself to a night or two at Lapa Rios, 45 minutes south of Jimñez, one of the most upscale lodges anywhere in the Costa Rican rainforest (doubles, $146 per person; 735-5130, fax 735-5179). After some excellent sea kayaking right off the beach or a horseback ride to nearby waterfalls, you'll want to take advantage of the lodge's massage service.
Rainforest-covered Caÿo Island, 13 miles offshore from Drake Bay, was used as a sacred burial ground by pre-Columbian Indians, who notedas park rangers do todaythat it's struck by lightning with unusual frequency. A $65 boat trip carries you to this uninhabited island and its centuries-old artifactsor those that remain. All over the island, depressions in the earth mark graves that were raided years ago. Caÿo's greatest appeal, however, lies off terra firma and beneath the sea. Though the waters here are not Caribbean-style clear, the marine life is abundant. A snorkeling trip can yield dozens of animal encounters, especially with moray eels and olive ridley turtles. If you're scuba certified, sign up with dive master Jos Marin, based at the Aguila de Osa, and watch as sharks and manta rays put on a floor show. A two-tank dive costs $110.