Known for its shallow reefs, dazzling color, and diversity of life, Cancún is one of the best places in the world for beginning scuba diving. Punta Nizuc is the northern tip of the Gran Arrecife Maya (Great Mesoamerican Reef), the largest reef in the Western Hemisphere and one of the largest in the world. In addition to the sea life along this reef system, several sunken boats add a variety of dive options. Inland, a series of caverns and cenotes (wellsprings) are fascinating venues for the more experienced diver. Drift diving is the norm here, with popular dives going to the reefs at El Garrafón and the Cave of the Sleeping Sharks -- although be aware that the famed "sleeping sharks" have departed, driven off by too many people watching them snooze.

A variety of hotels offer resort courses that teach the basics of diving -- enough to make shallow dives and slowly ease your way into this underwater world of unimaginable beauty. One preferred dive operator is Scuba Cancún, Bulevar Kukulkán Km 5 (tel. 998/849-4736; www.scubacancun.com.mx), on the lagoon side. Full certification takes 3 days and costs $410 (£226). Scuba Cancún is open daily from 7am to 8pm, and accepts MasterCard and Visa. For certified divers, Scuba Cancún also offers diving trips in good weather to 18 nearby reefs, as well as to Cenotes Caverns (9m/30 ft.) and Cozumel. The average dive is around 11m (36 ft.), while advanced divers descend farther (up to 18m/60 ft). Two-tank dives to reefs around Cancún cost $68 (£37); those to farther destinations cost $140 (£77). Discounts apply if you bring your own equipment. Dives usually start around 9:30am and return by 1:30pm. Snorkeling trips cost $27 (£15) and leave every afternoon at 1:30pm and 4pm for shallow reefs about a 20-minute boat ride away.

The largest dive operator is Aquaworld, across from the Meliá Cancún at Bulevar Kukulkán Km 15.2 (tel. 998/848-8327; www.aquaworld.com.mx). It offers resort courses and diving from a man-made anchored dive platform, Paradise Island. Aquaworld has the Sub See Explorer, a boat with picture windows that hang beneath the surface. The boat doesn't submerge -- it's an updated version of a glass-bottom boat -- but it does provide nondivers with a look at life beneath the sea. This outfit is open 24 hours a day and accepts all major credit cards.

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Besides snorkeling at El Garrafón Natural Park, travel agencies offer an all-day excursion to the natural wildlife habitat of Isla Contoy, which usually includes time for snorkeling. The island, 90 minutes past Isla Mujeres, is a major nesting area for birds and a treat for nature lovers. You can call any travel agent or see any hotel tour desk to get a selection of boat tours to Isla Contoy. Prices range from $45 to $70 (£25-£39), depending on the length of the trip, and generally include drinks and snorkeling equipment.

The Great Mesoamerican Reef also offers exceptional snorkeling opportunities. In Puerto Morelos, 37km (23 miles) south of Cancún, the reef hugs the coastline for 15km (9 1/3 miles). The reef is so close to the shore (about 460m/1,509 ft.) that it forms a natural barrier for the village and keeps the waters calm on the inside of the reef. The water here is shallow, from 1.5 to 9m (5-30 ft.), resulting in ideal conditions for snorkeling. Stringent environmental regulations implemented by the local community have kept the reef here unspoiled. Only a select few companies are allowed to offer snorkel trips, and they must adhere to guidelines that will ensure the reef's preservation. Cancún Mermaid (tel. 998/843-6517; www.cancunmermaid.com) is considered the best -- it's a family-run ecotour company that has operated in the area since the 1970s. It's known for highly personalized service. The tour typically takes snorkelers to two sections of the reef, spending about an hour in each area. When conditions allow, the boat drops off snorkelers and then follows them along with the current -- an activity known as "drift snorkeling," which enables snorkelers to see as much of the reef as possible. The trip costs $50 (£28) for adults, $35 (£19) for children, and includes boat, snorkeling gear, life jackets, a light lunch, bottled water, sodas, and beer, plus round-trip transportation to and from Puerto Morelos from Cancún hotels. Departures are Monday through Saturday at 9am. For snorkelers who just can't get enough, a combo tour for $30 (£17) more adds a bicycle tour to additional snorkeling destinations. Reservations are required at least 1 day in advance; MasterCard and Visa are accepted.

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Cancun Guide Info - Cancun Guide Info - Definitive guide to the Mexican Caribbean, including history, basic facts, getting there, getting around once you're there, accommodations, and what to see and do.
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Cancun Travel Guide - Cancun Travel Guide - offers hotel rentals in all major cities of Cancun.