Tulum is full of cenotes—natural pools where you can go swimming, often with caves. The Grand Cenote is one of the most well-known, because it’s great for families and well-equipped to handle visitors. You’ll find it off the side of the road near downtown Tulum (the entrance fee is 150 pesos or $10 USD). For an additional price, you can rent snorkel gear, life vests, and lockers. Visitors are required to shower before they enter, to keep the water clean of pollutants like sunscreen and bug spray. (Look out for a turtle area near the equipment rental that little ones will love.) The cenote itself is a series of caves connected by waterways, so you can swim from one end to another. And there are buoys to hold onto for less confident swimmers. Stay quiet in the caves to spot the bats, which sometimes fly overhead. The water is crystal clear, and you can see fish without having your head underwater. There are certain parts that are shallow enough to walk on, but beware of rocks, which are sharp in some places and moss-covered and slippery in others. Given its popularity, the cenote can get crowded (this is not a great place for diving), but it thins out on rainy days—this is an ideal activity for an overcast day.