Crystal-clear water and the second-largest coral reef in the world, located just off the coast of the Yucatan Peninsula, are a dream come true for divers and snorkelers, so it should come as no surprise that scuba diving and snorkeling are two of the most popular water sports in which visitors to Cancun participate.  There are an abundance of companies in Cancun that offer snorkeling trips and scuba diving excursions, and the number of great spots to dive or snorkel are countless.  

Cozumel is one of the world's best places for scuba diving — Photo courtesy of Skinned Mink

During a one-week vacation, a person could easily snorkel or dive every day and see a new place each time. The Cancun Underwater Museum has over 450 statues on the sea floor, spread over two locations. One location is off the coast of Isla Mujeres, a tiny island paradise, just a few miles north of Cancun's mainland, and the other locations is at Punta Nizuc, in the southern portion of Cancun's hotel zone. Both of those spots require very little travel time and could probably be seen in one day, but while you are so close to Isla Mujeres, it would be a shame to not visit the beautiful island for a meal, a few beers, or just to take in a gorgeous sunset from Playa Norte (North Beach).   

Puerto Morelos, a small fishing village roughly 20 miles south of Cancun, has a coral reef just a few hundred yards from shore.  The Puerto Morelos National Reef Park is a fantastic place to dive or snorkel without spending all day on a boat, or traveling in a bus. To ensure that the reef is properly protected, people are not allowed to swim out to the reef from shore, or to go out to the reef in their own boat. Everyone must book a snorkel or dive excursion with a local tour operator.

Once you make your way out to the reef, you will be wowed by the number of tropical fish you see and you might even catch a glimpse of a sea turtle while exploring the marine park's incredible undersea world. Puerto Morelos is a charming little town with seaside eateries, a small town square, and a tilted lighthouse (there is also a newer lighthouse that stands upright). Like Isla Mujeres, you should linger in this small town for a while, after your undersea adventure.   

The best place in the area for snorkeling and diving is Cozumel. Jacques Cousteau discovered this underwater wonderland back in the sixties and it's still one of the world's most spectacular venues for diving today. Chankanaab National Park is on Cozumel's west coast and that is one of the island's best spots for diving. Cozumel can be reached by ferry from Playa del Carmen (it's approximately a 45-minute ferry ride), if you wish to make the trip on your own, or you can book a tour with a dive company and drive to Playa del Carmen or Puerto Aventuras and then take a boat over to the reef. Playa del Carmen is about an hour south of Cancun, so hard-core divers may opt to spend a few days on Cozumel instead of just trekking over for a few hours.   

Kin-Ha cenote is just one of many natural, underground springs in the Riviera Maya — Photo courtesy of Brian Valdes

In addition to open water dives, the Yucatan Peninsula offers some rather unique experiences for snorkelers and divers. The Riviera Maya region is home to the world's longest underwater river system and many cenotes (natural springs) are connected to the underwater rivers. Experienced divers can explore the area's cenotes and the underwater rivers, but this is definitely something you want to research before taking the plunge because with hundreds of kilometers of underground waterways, it's very easy to get lost. Cenotes can be very deep, so they may not all be fun or interesting for snorkelers, but divers are likely to have a ball in them.

Swimming with whale sharks is one of the most popular summer activities in Cancun — Photo courtesy of Brian Valdes

Finally, another uncommon activity that can be done in Cancun, or the Riviera Maya, is to swim with whale sharks. During the summer, whale sharks, the world's largest fish, migrate to the warm water near Cancun. Excursions to swim with the gigantic fish (they are not a threat to humans, despite having the word "shark" in their name) are incredibly popular. Most people just use snorkeling gear while on these excursions because the whale sharks often swim near the surface of the water, but scuba divers can also book dive trips to see whale sharks. This is an all-day tour, but this once-in-a-lifetime experience is well worth the travel time.