Costa Rica's underwater wonders range from coastal coral reefs to offshore islands. Those varied dive spots contain diverse and beautiful marine life that includes giant manta rays, timid sea turtles, colorful angel fish, intricate coral formations, psychedelic sea slugs, spiny puffer fish, delicate sea fans, curious dolphins and, on rare occasions, whales.

Though the country's waters contain enough marine life to please the most experienced of divers, you need be little more than a curious swimmer to catch a glimpse of some underwater sights, since there are plenty of spots that are perfect for snorkeling. Costa Rica is also an excellent place to learn how to scuba dive, since most dive centers offer inexpensive certification courses in English that can be completed in less than a week.

There are several excellent snorkeling areas along the southern Caribbean coast. The country's largest coastal reef is protected within Cahuita National Park, south of the town of the same name, where you can rent snorkeling equipment and hire people to take you out in boats. The point at Puerto Viejo, south of Cahuita, also has a coral reef wrapped around it that makes for convenient diving. Punta Cocles and Punta Uva, two points to the south of town, have healthier coral formations with plenty of fish around them. Manzanillo, a small fishing village a few miles further south, also has diving off shore. There are also a few good dive spots near the city of Limon, such as the water surrounding Uvita Island. The best visibility in the Caribbean is from March to early May and from mid August to mid November, but water quality can change from day to day.

The Pacific has the country's best diving, with less coral, but plenty of big fish. The most popular Pacific diving area is the northwest, where dive centers in Playa del Coco, Ocotal and Hermosa offer trips to several spots in the Culebra Bay and the Bat Islands (Islas Murcielagos), to the northwest, where divers often see sharks and manta rays. The dive center in Flamingo usually takes people to Santa Catalina Island, about five miles off shore, which is another good spot to see sharks and other big fish. The best visibility and water temperatures in the northwest are found from June to September, though the conditions can change from day to day.

There is good snorkeling in Curu National Wildlife Refuge, and near the beach resorts of Tambor and Montezuma. There is also usually good snorkeling off the second beach in Manuel Antonio National Park, and around the points and islands between Dominical and Marino Ballena National Park. However, the best diving off the Pacific coast is found at several underwater reefs near Caño Island, which can be explored on dive trips offered by some of the lodges in nearby Drake Bay. Contrary to the northwest, the best visibility in the waters around Caño occurs during the dry season, though the water tends to be pretty clear year round.