The best beaches in San Juan are at Isla Verde and Condado, both backed by a fortress wall of high rises. If you want to get out of the city (though not away from the crowds) try picturesque Luquillo, 30km (19mi) east of the capital, which is backed by nothing more intrusive than palm trees. The beaches on the southern coast are more sheltered and have calmer water for swimming than those on the northern Atlantic coast. In the south, there's a gem at Punta Guilarte near Arroyo. The west has a whole series of great beaches; the pick of the bunch is popular Boquerón. If you're exploring the islets off Puerto Rico, Flamenco Beach on Culebra regularly makes most people's regional top 10 list.

The best dives off Puerto Rico are a couple of kilometers offshore, since water visibility nearshore is often clouded by river runoff. Legendary Desecheo Island, west of Rincón, is perched on the edge of a 9km (5mi) deep submarine canyon and is regarded as one of the ultimate Caribbean diving destinations. Other top sites include La Parguera, off the southwestern coast; the islands of Culebra and Vieques, off Fajardo; Humacao, south of Fajardo; and Mona Island, a six-hour boat trip from Mayagüez. Sections of the northwestern coast near Isabela and Aguadilla offer shore diving, but water conditions can be rough and visibility poor.

You'll also need to hire a boat to reach the very best snorkeling sites. There's a number of spots on the southwestern coast, notably around La Parguera. Other superb spots are the deserted islet of Palomenitos, off the coast of Fajardo, and Mona Island. For something completely different, it's definitely worth renting a boat or kayak to see the nightly displays of bioluminescence at Phosphorescent Bay near La Parguera and at Esperanza on the islet of Vieques.

The best surfing is along the northwestern stretch of coast between Rincón and Isabela between October and April. Serious windsurfers arrive in winter to take advantage of the swells on the northern Atlantic coast, particularly at Isla Verde. Rincón and Jobos near Isabela are also pretty hot, though beginners prefer the sheltered waters of San Juan's Condado Lagoon. If you're interested in sailing, Fajardo is the main yachting marina, and there are plenty of boats for hire. San Juan is the main deep-sea fishing charter port. There's world-class marlin, tuna and sailfish in the waters off the capital.

There are hiking opportunities galore in the island's interior, particularly in the rainforest of El Yunque, in the karst region of Río Camuy Cave Park and, for birdwatchers, in the coastal mangroves of the Guánica Reserve on the southern coast. If birds ain't big enough, there's humpback whale watching from Rincón between January and March.

Experienced cavers can explore the extensive underground sections of the Camuy River system with National Parks guides. Novices can take an expensive trolley-tram that accesses one cave via a sinkhole - be aware that weekends are so crowded that the experience is more rush hour transit than restful nature. Cockfighting may not be your idea of a relaxing Sunday afternoon, but if you have a strong stomach and want to see what excites the locals, fights take place in galleras in most country towns. The more sedate sport of kite flying is popular on the grassy, breezy slopes surrounding El Morro in San Juan, said to be the world's best kite site.

Every Puerto Rican town celebrates its saint's day, often with a mixture of pagan and Catholic iconography and Indian, African and Spanish traditions. There are solemn religious aspects and plenty of feasting, music, dancing and colorful costumed processions. One of the best is the Festival of St John the Baptist in San Juan in late June, which wonderfully fuses the religious and the secular. The highlight of the parade is a communal luck-enhancing midnight walk backwards into the sea. Worth a detour are Mayagúez's twinkling La Virgen de la Candelaria in early February and Loíza's jubilant St James Festival, which takes place late July and celebrates the town's multicultural heritage.

Old San Juan takes to the streets during the Saint Sebastian Street Festival in the third week in January. Ponce, where revellers dress up in horned masks for dancing and parades, is the best place to celebrate Carnival in February. In June San Juan's Casals Festival honors the famous cellist who came to call Puerto Rico home. It attracts classical musicians of international repute and is one of the Caribbean's major cultural events. Puerto Ricans get baseball fever when the season starts in November, reaching its climax in February.

Las Navidades between 15 December and 6 January is the peak period of socializing and religious observation, though many of the celebrations take place at family homes. Not so the riotous Festival of Innocents in Hatillo on 28 December, when masked and costumed participants chase kids through the streets in memory of Herod's bid to wipeout baby Jesus. Look out for parrandas, wandering bands of minstrels and revelers, around Christmas time.