Xel-Ha is an eco-park about an hour and 15 minutes south of Cancun. We chose to take an option from Olympia Tours that included the morning in Tulum, with the afternoon in Xel-Ha. Olympia also has a full day Xel-Ha option. Another option Olympia offers is an all-inclusive package at Xel-Ha. This included meals, snorkel equipment, beverages (alcohol included), towel rental, and locker rental.
The main attraction at Xel-Ha is the 10-acre lagoon, where you can snorkel, tube or just go for a dip. We brought our own snorkel gear, but we did wait on line for the free life jacket rental. The lagoon is anywhere between 9-12 feet deep, with most fish congregating by the rock formations scattered about the lagoon. The tropical fish pay no mind to you as you admire their beauty in their natural environment. One great area to see larger fish, such as snapper, is to snorkel by the floating bridge, where the Xel-Ha people throw feed into the lagoon.
Another option at Xel-Ha is the "Swim with the Dolphins." To swim with the dolphins costs a fee of about $115. If you plan on this you should make reservations at least 24 hours in advance. You can also watch the dolphins around the fenced area as they play with the paying customers.
A popular area in Xel-Ha is the "Hammock Park". Here you can just relax or take a nap on one of about 50 hammocks. Next to "Hammock Park" is a picture taking area. Here you can take pictures with beautiful Macaw parrots. The handler will place as many as three on your head and arms. To take a picture is free, but if you want the picture it will cost about $9. Be smart have your camera ready to take a picture quickly and you can save yourself a couple of bucks.
Other areas of Xel-Ha include an underwater cave. This was very cool. The cave is in a "U" shape and is not very big. There is also a Xel-Ha employee there to take a picture of you for a price. Here is a quick tip. There are sinkholes on a trail over the cave. Here you can see down into the water, get a family member or friend to take a picture of you as you swim by the hole. Along one of the trails (on the trails you will see plenty of iguana, so watch your step) you will come to a Tarzan swing. You can also get your picture taken here by a Xel-Ha photographer (they also take pics of you as you swim in the lagoon).
Your food options in Xel-Ha are decent. There is a buffet, a couple of sit-down restaurants, and a couple of fast-food places, if I remember correctly. There are also a few ice cream stands around the lagoon.
I would say Xel-Ha was one of the highlights on our trip to Cancun.