Cancun's beaches - the pristine turquoise waters in Cancun are incredibly inviting for swimmers and water sports. Many of the all-inclusive resorts in Cancun provide free non-motorized water sports and can suggest companies who offer services such as jet ski rental and parasailing.
Golf - Cancun is a fantastic place to golf. Some resorts, including the Hilton and the Moon Palace, actually have their own golf courses. World renowned golfer Jack Nicklaus actually designed several of Cancun's golf courses.
Snorkeling and SCUBA - the Maya reef is the second largest in the world, behind Australia's Great Barrier Reef, and is a haven for snorkelers and divers.
Ecological parks - Cancun and the Riviera offer several amazing ecological parks, including Xel-Ha Natural Aquarium, Xcarat Ecological Park and Garrafon Natural Park. Explore these parks' underground rivers, swimming and snorkeling areas, wild animals and natural aquariums.
Swim with the dolphins - one of the Caribbean's most popular activities, there are plenty of opportunities to swim with dolphins in Cancun.
Mayan Ruins - The Yucatan Peninsula has some of the world's most fascinating Mayan Ruins. Many of the ruins are still in quite good condition. Plenty of tours that run from Cancun to the ruins on a daily basis and these can be booked ahead of time or often from your hotel.