Gray Line Cancún. Cancún's Gray Line office can customize your vacation, offering everything from luxury airport transportation and dolphin adventures to sunset dinner cruises and tours of Chichén Itzá. 877/240–5864; 998/887–2495; 01800/719–5465 toll-free in Mexico. www.graylinecancun.com. From M$680.
Olympus Tours. Specializing in outings around Cancún, this agency’s options run the gamut from ATV and horseback tours to cenote excursions and cultural encounters. It will also book reservations for Xcaret, Xel-Há, and other area adventure parks. Av. Yaxchilán, Sm. 17, Lote 13, Mza 2, El Centro, Cancún, Quintana Roo, 77500. 998/881–9030; 786/338–9358 in the U.S. www.olympus-tours.com. From M$750.
AquaWorld. In addition to Nichupte lagoon tours and Isla Mujeres day trips, AquaWorld’s sightseeing menu includes unusual options like the B.O.B. Adventure. Short for Breathing Observation Bubble, B.O.B. lets you steer through the reefs on a machine that resembles an underwater motor scooter (a pressurized helmet allows for normal breathing). Tours on the Paradise SubSee are another alternative. This "floating submarine" is a glass-bottom boat that submerges halfway into the water. On the short journey to Punta Nizuc, you'll see turtles, fish, coral, and a few statues in the Underwater Museum. Blvd. Kukulcán, Km 15.2, Zona Hotelera, Cancún, Quintana Roo, 77500. 998/848–8327 or 877/730–4054. www.aquaworld.com.mx. B.O.B. M$920; SubSee Explorer from M$544; other tours from M$817.
Asterix Tours. This is one of the only companies permitted to depart from the Zona Hotelera on tours to Isla Contoy and the underwater gardens of Isla Mujeres. Trips to the former leave at 9 am and return at 5 pm on Tuesday, Thursday, and Saturday; ones to the latter leave on Wednesday and Friday. Day- and nighttime fishing trips run three times a week. Blvd. Kukulcán, Km 5.5, Zona Hotelera, Cancún, Quintana Roo, 77500. 998/886–4270. www.contoytours.com. Isla Contoy tours M$1827; Isla Mujeres tours M$1287; fishing trips M$1111.
Kolumbus Tours. Excursions to Isla Contoy are available Thursday and Sunday on a double-decker trawler; you can also choose a daily catamaran tour that combines Isla Contoy and Isla Mujeres. Punta Conoco 36, Sm 24, El Centro, Cancún, Quintana Roo, 77500. 998/884–5333; 01800/715–3375 toll-free in Mexico. www.kolumbustours.com. From M$1294.
Sea Passion Catamaran. Day trips to Isla Mujeres (which include a buffet lunch, open bar, and snorkel equipment) are available by reservation. Chac-Chi Marina, Blvd. Kukulcán, Km 3.2, Zona Hotelera, Cancún, Quintana Roo, 77500. 998/849–5573. www.seapassion.net. From M$1089.