Sure, you could spend your vacation in Puerto Rico slurping pina coladas by the hotel pool, then return home crimson-faced, a few pounds heavier and with no exciting tales to tell.

But those yearning for more than a run-of-the-mill resort experience can explore caves, dive with sea turtles, swim in bioluminescent bays, hike through the rainforest and still get good cocktails. Few Caribbean islands offer as many outdoor adventures as this popular destination.

Rappelling and Caving

Put on a life jacket, harness, lamped helmet and get ready to explore the Camuy Caves, the third largest cave system in the world.

Rappelling down 250 feet (about the height of a 25-story building) into the mouth of an enormous cave is no amateur stuff, so you'll need an experienced guide. Aventuras Tierra Adentro organizes group expeditions, leaving from a central location in San Juan. Inside the caves, after you're done admiring the stalagmites and stalactites, jump on the underground rivers for a cool body-rafting experience.

Surfing

Rincón, on the western coast, is the island's surfer hangout. Catch the best waves from October to February, on beaches surrounding the Punta Higueras Lighthouse. You can sign up for daylong classes with

Rincón Surf School, an established company that also runs a small guesthouse. If you're in a splurging mood, stay at the

Horned Dorset Primavera, a chic, Mediterranean-inspired hotel with suites starting at $600 a night.

Diving and Snorkeling

Head to La Parguera, in the southwest, for world-class diving and snorkeling. A 20-mile-long coral-reef cliff known as The Wall, which drops 90 feet into the sea, is home to octopuses, giant sponges, sea turtles and other interesting fauna. Many local operators, like Paradise Scuba and Snorkeling, take you out there for the day. If you'd like to stay longer, or want to become a certified diver before plunging,

Coparamarina Beach Resort has its own staff of dive masters and a yacht ready for deep-sea trips.

At night, go for a swim in the nearby bioluminescent bay. Make sure you choose a boat operator who will drop anchor for a while and let you take a leisurely dip. Prepare to glow.

Hiking and Camping

A 45-minute drive east of San Juan, you'll find El Yunque, the only tropical rain forest in the National Forest System. With 240 species of native trees and more than 100 animal species, including the green mango hummingbird and the elusive Puerto Rican parrot, it's also one of the most biologically diverse forests in North America.

Large sections of El Yunque's 28,000 acres are accessible through man-made trails (veering from these trails is strongly discouraged -- even experts have disappeared without a trace inside the dense shrubbery). Choose one of the more challenging, children-free hikes, such as El Yunque trail, which takes more than two hours each way and rises to 3,445 feet.

You'll pass through lush canopies and cool mountain streams and eventually reach the mysterious-looking Dwarf Forest, always shrouded in clouds and populated by stunted trees. If you go very early in the morning, the peak will be clear enough to offer panoramic views of the surrounding forest, the Atlantic Ocean to the north and the Caribbean sea to the east.

If you're in for a primitive camping experience, the park allows visitors to sleep over. Free passes are offered daily before 4:30 p.m. at the Palo Colorado station. For more information, call (787) 888-1880.

Paola Singer is a freelance writer based in New York City. She has written for The Wall Street Journal, Newsday and Hemispheres magazine.