Akumal Bay—the one right in front of town—has a long, slow-curving shoreline, with soft sand shaded by palm trees. The water is beautiful but a bit rocky underfoot, and you should be aware of boat traffic when swimming or snorkeling.
Half Moon Bay also can be nice for swimming and snorkeling, but the shoreline is rocky in some places; consider wearing water shoes to help you ease into the water.
At the mouth of an elbow-shaped lagoon at the north end of Akumal , an endless upwelling of underground river water collides with the tireless flow of seawater—the result is a great place to snorkel, teeming with fish and plants adapted to this unique hybrid environment. Once a secret snorkeler’s getaway, Laguna Yal-Ku (8 a.m.–5:30 p.m. daily, US$9 adult, US$6 child ages 4–12, free age 3 and under, US$15 snorkel gear, US$2 locker) now has a spot in every guidebook and tour group itinerary—come before 10 a.m. or anytime on Sunday for the least traffic. (That, and a shot at snagging a private picnic area [US$20], complete with palapa shade, a table, and chairs, if you want to make a day of it.)
You can snorkel in the lagoon’s broad mouth or up the narrow channel to its source. If possible, use a T-shirt or wetsuit instead of sunscreen—even the biodegradable kind can collect on plants and coral. The lagoon is dotted with various intriguing bronze sculptures by Mexican artist Alejandro Echeverría.
Next to Akumal Dive Shop, the Akumal Ecological Center (CEA, tel. 984/875-9095, www.ceakumal.org , 9 a.m.–1 p.m. and 2–6 p.m. Mon.–Fri.) is a nonprofit founded in 1993 to monitor the health of Akumal’s ecosystems, particularly related to coral and sea turtles. During turtle nesting season (May–July) you can join CEA volunteers on nighttime turtle walks, covering about two kilometers (1.25 miles) of beach, looking for new nests and helping move eggs to protected hatcheries.
From August to October, visitors can help release a batch of hatchlings into the sea (9 p.m. Mon.–Fri.). Stop by the center for more details and to sign up; turtle outings and activities are free, but a US$10 donation is appreciated. The center also has free displays and frequent evening lectures on ocean ecology in the high season.
CEA also operates long-term volunteer projects on reef monitoring, sea-turtles monitoring, and environmental education projects. Volunteers stay in the center’s comfortable dorms, with kitchen and Internet access; minimum age is 21, and some fees are required. See the website for details.
Maya for Cave with an Underground River, Aktun Chen (Hwy. 307 Km. 107, tel. 984/806-4962, www.aktunchen.com , 9 a.m.–5 p.m. daily, summer until 7 p.m., last tour one hour before closing, US$26 adult, US$14 child under 10) is certainly that, and more. Admission adds up fast, especially for families, but the experience is definitely memorable. The cave system has a breathtaking array of stalactites and stalagmites, and a 12-meter-deep (40-foot) cenote filled with crystalline water at the end; lighting and a pathway make it accessible to all.
Leaving the cave, you can check out the park’s numerous animal enclosures, with spider monkeys, toucans, and more; there also is a kilometer (0.6 mile) of zip lines, plus a cenote for snorkeling. Tours are offered in English and Spanish and last about 90 minutes. Most hotels offer trips here that include transportation, or you can go independently—look for the turnoff just across from Aventuras Akumal, and continue three kilometers (1.9 miles) to the entrance. Mosquito repellent and a bottle of water are recommended. You’ll encounter the least crowds before 11 a.m. and on weekends.