Part of the Xcaret nature-adventure park group, Xel-Há (pronounced shel-hah) is a natural aquarium made of coves, inlets, and lagoons cut from the limestone shoreline. The name means "where the water is born," and a natural spring here flows out to meet the salt water, creating a unique habitat for tropical marine life. There's enough to impress novice snorkelers, though there seem to be fewer fish each year, and the mixture of fresh and salt water can cloud visibility. Low wooden bridges over the lagoons allow for leisurely walks around the park, and there are spots to rest, swim, cliff–jump, zip-line, or swing from ropes over the water.
Xel-Há gets overwhelmingly crowded, so come early. The grounds are well equipped with bathrooms and restaurants. At the entrance you'll receive specially prepared sunscreen that won't kill the fish; other sunscreens are prohibited. The entrance fee (M$1,206) includes a meal, towel, locker, inner tubes, and snorkel equipment; other activities like scuba diving, zip-lining, swimming with the dolphins, and spa treatments, are available at additional cost. Discounts are offered when you book online.