When the pop anthem "Living la Vida Loca" kidnapped the airwaves back in the late '90s, you might have thought that Ricky Martin, arguably Puerto Rico's most famous export, was referring to the diving in his native island. And for good reason. Puerto Rico's topography, both under water and above, is an exhilarating, unpredictable crazy quilt of diversity. The same ages-old volcanic activity that created the island's topside terrain, which is lush and mountainous in parts and barren and flat in others, can also take credit for the epic underwater landscape, with its heady, vertigo-inducing drop-offs and networks of caves and tunnels.

Thanks to this extraordinary geography, Puerto Rico, the smallest of the Greater Antilles — it's roughly the size of the state of Connecticut — offers a wide range of diving opportunities. And its favorable location straddling the semi-protected Caribbean Sea and the open Atlantic means that divers get the best of two ecosystems, with sheltered reefs on the one hand and pelagics from the deep beyond on the other.

Diving takes place on all sides of the island, depending on your skill level and whether your preferences lean toward sheer walls, historic wrecks, coral reefs, animal encounters or mangroves. For new divers, Puerto Rico's eastern beaches, especially those on the little islands of Vieques and Culebra, are a logical first stop because they're bathed in calm seas. Off Fajardo, in the northeast, are top sites for reef and cave diving, easily accessible from the capital, San Juan. And off the west coast lies dramatic Tourmaline Reef, home to orchards of black coral and masses of reef fish, as well as two more must-dive islands, Mona and Desecheo.

22-Mile Wall

I've come to Puerto Rico to dive its rugged southwest coast. Along with a group of 19 divers who have traveled from as far as Austria to participate in a special Scuba Diving expedition, I'm here to check out the area's main attraction: the famed 22-mile wall. About two miles offshore, a spectacular series of slopes and sheer drop-offs starts as shallow as 30 feet and then disappears into a 2,000-foot-plus abyss.

On our first day, I board the dive boat and listen to the captain brief us on the day's agenda. We'll be diving a site on the wall called Fallen Rock. Thousands of years ago, a massive portion of an underwater promontory broke off and fell into the depths, carving a deep cut. Today this protected crevice is lush with corals, invertebrates and schools of fish seeking sanctuary from currents and the large predators that patrol the blue water a few yards away.

The Puerto Rican government has allowed the placement of several buoys along the wall, and one of these marks the Fallen Rock drop-off. I descend 50 or 60 feet, but instead of heading for the lip of the wall, I'm distracted by the residents of the coral heads. Pairs of squid, octopuses and a free-swimming remora conspire to keep me entertained in the sandy flats. By the time I reach the wall, I'm well into my dive, and it would be unwise to investigate the sponges that beckon from deep below. I meander back to the coral heads, where I find the octopus still in its hiding place, and I spend the rest of the dive watching the cagey cephalopod. After a sun-drenched surface interval, we make a second and then a third dive. It's the ideal introduction to Puerto Rican diving and the inhabitants of its clear, warm waters.

Guanica Dry Forest

That afternoon, I hike through Guanica Dry Forest, a United Nations International Biosphere Reserve filled with barrel cacti and bushy gumbo-limbo trees. Very little of the world's subtropical dry forest remains intact, and now this rare ecosystem is in my backyard. The dry forest of Guanica differs dramatically from the wet forest of the central mountains and north coast of Puerto Rico. The steep 4,400-foot-high mountains of the Cordillera Central form the backbone of the island, blocking the rain clouds that come from the northeast. Thus, while the green, northern side of the island enjoys plenty of rain, the southwest remains dry.

Arid as they are, the forests of Guanica still support more than 600 plants and a variety of animals. Darwinism is alive and well here: The plants that manage to thrive — ironwood, buttonwood mangrove and milkweed — do so by toughing it out. Many have adapted to the low rainfall, salt water and wind by developing deep roots and fleshy leaves.

On my second dive day, we cruise over to Pozas, an island reef with sculptural coral heads and a labyrinth of arches and swim-throughs. At 55 feet, the rock protuberances are covered with inverts; nudibranchs and sea cucumbers populate the nooks and crannies. The clear water and bright red encrusting sponges plating the corals make an ideal photographic backdrop. I should be taking pictures, but I'm too busy watching schools of fish part in front of me and close back in after I pass. Clusters of grunts hang motionless, except for the ebb and flow of the sea. Occasional angelfish sashay past, as do large sea turtles. I watch a renegade barracuda use the shadow cast by our dive boat as a cloaking device. Unsuspecting smaller fish will surely be eaten, and I want to stick around for the action.

Return to Fallen Rock

The Next morning, my dive boat makes an early call to revisit Fallen Rock. Now a veteran, I want to explore the depths of the wall and re-examine the octopus lairs. At the lip of the wall, I kick down past about five ledges, each a habitat showcasing a different dA(C)cor.

The first is shabby-chic, with massive sponges and detailed coral sculptures strewn haphazardly, while fish of clashing colors mill about. I drop down to 120 feet, where the water is significantly colder and darker. The ledge there is a plateau with a perpendicular wall, riddled with hundreds of rope sponges, each a different color and length. Some are short and stubby; others are long spirals that stretch into the blue. Perhaps it's the narcosis talking, but I'm reminded of a medieval torture room, with manacles and restraints sprouting from the wall. It's definitely time to ascend.

I slowly work my way up the wall and glide over the lip. At 60 feet, I still have plenty of air, so I decide to call on the octopus. I easily find the hollowed-out coral head the creature calls home. Telltale shells from recent crustacean dinners confirm that my internal GPS is correct. I maneuver to the front of the lair and gently settle into the sand. There he is, halfway out of the hole. He stays very still for a few moments and then continues his housecleaning, tossing shells to and fro. Because octopuses are nocturnal, this kind of daytime activity is extremely rare, so I keep the bustling cephalopod in view for the rest of my dive.

Into the Mangroves

After the deep dive, I decide to stay shallow and visit the mangroves that line the Guanica coast. Many people snorkel in this shallow biome, but I do a lizard-like crawl in full scuba gear, gently pulling myself along with my fingertips--no kicking, because this could create zero visibility in an instant. Slowly, I pull myself into a cove barely wider than my body. Then I stop. I have a five-minute rule in mangroves: When you first arrive, you won't see anything. The creatures have all scurried into the deep pockets of the grove, and the darkness under the tree roots requires that you give your eyes time to adjust. But stay perfectly still for five minutes and you will see the area come alive. Leaves inches from my fingertips begin to swim away, revealing their secrets of stealth, and the juvenile fish return, playing follow-the-leader through the intertwined roots. As my eyes focus on what I think is a sponge, I realize it's actually an amber seahorse. I slowly pull myself out of the shallow grass, and am treated to a final mangrove encounter: heading straight toward me is a spotted snake eel.

After sunset, a group of us set out in a small wooden boat from nearby La Parguera for a night dive in bioluminescent Bahia Fosforescente (Phosphorescent Bay). I know we're nearing the bay when the rickety 25-horsepower motor kicks up enough light to illuminate the captain's face. The boat slows down, and it's time to backward-roll into the glowing water. I watch my fellow divers take the plunge, making radiant water angels on entry. Then it's my turn to join the living light show. I roll in and, if only for a moment, become part of Puerto Rico's underwater vida loca.

Puerto Rico's Island Escapes

Puerto Rico's satellite islands are getaways in every sense of the word. Situated just off the mainland, these unique offspring hit all the marks on every diver's wish list--wrecks, reefs, walls and big fish action--in pristine and secluded settings.

CULEBRA > All the action in little, laid-back Culebra is below the waterline. Divers have a choice of tunnels, drop-offs, caves and wrecks. Most sites are easily accessed via 30- to 40-minute boat rides and are relatively shallow, at 20- to 75-foot depths. Where: Twenty miles off the east coast of Puerto Rico, Culebra is reached by a short plane ride from San Juan or a ferry from the coastal town of Fajardo. Conditions: With no freshwater runoff, visibility often tops 100 feet. Topside Attractions: Kayaking, windsurfing and sailing are popular activities around Culebra. Snorkeling is best on Culebrita, the largest cay off Culebra, which is known for spectacular white sand beaches. Best Dive: The Wit Power, a 90-foot-long tugboat, sits in just 40 feet of water close to shore. Sunk in 1984, this richly encrusted vessel swarms with groupers, wrasses, angelfish and hawksbill turtles.

DESECHEO > Surrounded by dramatic drop-offs, Desecheo offers some of the best visibility — 70 to 80 feet — in the territory. Topside, this 19-acre preserve is home to monkeys and goats. Under water, expect a thriving community of reef creatures and visits by humpback and pilot whales January through March. Where: Fourteen miles west of Rincon, off the west coast of Puerto Rico. Some of the best encounters occur during the 50-minute boat trip from the mainland, so keep an eye out for pilot whales, mantas and dolphins. Conditions: Shallow fringing reefs and deep water with excellent visibility. Topside Attractions: The island is a National Wildlife Refuge, but visitors are not allowed on land due to unexploded ordnance. Best Dive: Colorful Yellow Reef is considered one of the best dives off Desecheo for sheer diversity of marine life. A wall descending to 100 feet leads to caves, but beware of occasional strong currents and surges.

MONA > Called "The Galapagos of the Caribbean," Mona Island is an isolated nature refuge, populated by boobies and iguanas, that is a favorite of naturalists and scientists. With a vibrant reef and diverse sea life, it is also superb for divers. Where: Mona is located 50 miles west of Puerto Rico. Because it's a refuge, permits must be obtained from the Department of Natural and Environmental Resources prior to visiting the island. Your best option is to go with a tour operator who can arrange transportation, food, water, camping equipment and the requisite permits. Conditions: Mona offers the best visibility in Puerto Rican waters, often up to 150 feet. Topside Attractions: Mona is 100 percent pristine nature. If you're looking for tourist amenities, this is not the place for you. Best Dives: The whole island. Reefs, walls and caverns in clear water make for unlimited diving opportunities. More than 200 species of reef fish, as well as dolphins, whales and sharks, have been sighted in these waters.

VIEQUES > A favorite of low-maintenance, independent travelers, Vieques offers glorious diving in a get-away-from-it-all atmosphere. For more than 60 years, the U.S. maintained a hotly debated naval base on the island, but with its closing in 2003, visitors now have greater access to many idyllic beaches and dive sites. Where: Eight miles off the east coast of Puerto Rico, Vieques is easily accessible by either a short flight from San Juan or via ferry from Fajardo. Conditions: Conditions vary around the island, but 60-foot vis can be expected, and currents are minimal. Topside Attractions: Vieques' main cultural draw is the El Fortin Conde de Mirasol museum, a restored 1840s fort that now offers a window onto the island's rich history. There's also a nightly light show at Mosquito Bay, a bioluminescent cove that glitters exquisitely when the millions of tiny dinoflagellates in residence are disturbed by movement. Best Dives: The top sites are found in the shallow fringing reefs off the island's south shore. Check out Patti's and Angel reefs, and don't miss Blue Tang Reef, known for its coral structures, giant barrel sponges, schools of reef fish and patrolling pelagics.

Travel Guide

Water Conditions > Average water temps are 85 degrees in the summer and 75 degrees in winter. Average visibility is about 60 to 80 feet and sometimes greater at offshore dive sites.

Climate > Temps average 85 degrees in the summer and 83 degrees in the winter.

Money Matters > The U.S. dollar is the local currency. Credit cards are widely accepted and ATMs are available in tourist areas. There is no departure tax.

Time > Puerto Rico is in the Atlantic Time Zone (one hour ahead of Eastern Time), but does not observe Daylight Saving Time.

** Electricity >** 110 volts, 60 cycles. European appliances require an adapter.

Language > English and Spanish are both official languages.