It used to be a public park of sorts, but that is a thing of the past in this area. The National Parks have been privatized and all of the river mouths and truly beautiful places along this coast have been developed into "Eco Parks". Theme parks of a sort. A word on all that:
First of all, "Ecology" has become the word to conjure with on this coast, like "organic" was in the seventies. (Just as adding brown sugar to soda pop made it "natural", here you strip mine a mountain for silver, but if you make it into dolphins, it's "ecological": Cancun recently held an "ecological art exhibit" in which sculptures were sunken in the bay, requiring SCUBA equipment or their nifty glass submarine to see them.) So it's a fairly meaningless term in the local context--although sufficient to suggest that what you will see was created naturally and not just poured out of cement truck, although even that line gets blurred at times. There is even a car rental company that advertises itself as "The Ecological Company". Okay, if you accept automobiles as ecological, and private car rentals instead of collective transport as being in the service of the planet, you will not be upset to find that your "Eco Park" features self-guided jungle tours on jet skis or motorcycles.
The privatization is another notable factor. "Privatization" was a big buzzword in the last administration. It was basically a scam, one aspect of the PRI party's raping of the country. You take a highway or airport built with tax dollars (or refinery nationalized from Standard Oil) and sell it off to private business--the government saves expense, everybody in sight skims a ton of graft, somebody gets their very own tollway or airport or park to run for profit. Perfect application of modern "neoliberal" eco-political principles by one of the world's perfect political machines.
The thing is, is it so bad a way to handle parks? The Mexican government can't really afford to run something like Xel-Ha the way the U.S. government runs, say, Yosemite. And even there, we have seen a slow increase in user fees and private concessions. Mexican National Parks have been generally rather tacky, poorly provided, and inadequately protected. So you turn the thing over to a local version of Disney and what do you get? Well, you get this beautiful, landscaped place with every possible facility and scientists taking care of stuff. Nice restaurants, clean bathrooms. You also get to pay $10-40 dollars to get in. With additional fees for special stuff like eco-blasting through jungle on motos. Or $35-80 US to swim and do tricks with dolphins.
So what you end up with is: the government saves money, the park is better kept, tourists pay about what they'd expect (and much less than Sea World or Six Flags--for now), and a lot of local people make a decent living. The only real losers are the local people who can't afford to go. And the thing is, most of the local people never had all that much yen to go snorkeling in underground rivers. But still, it's kind of a gyp for them. They don't mind though--they prefer having money come into the area. So. EcoParks, scam or public service? It's your call.
One thing's for sure, these are some way beautiful parks.
Xel-Ha, the first big privatization, is very close to Tulum and absolutely worth a visit for anybody who ever liked what they saw though a diving mask. An incredible place that has been totally exploited without being totally ruined. About $19 admission. Check out their website. The same folks took over the National Park at Garrafon, on Isla Mujeres, which is a good place to visit for a decent price, around $10 US for a day.
Xcaret is the best known of the parks, and the most flamboyant. Anything I've said here goes double for Xcaret. Mayan wonderland, jungle safari, undersea wonderment, dance shows, you name it. $39 US gets you in, but it'll cost a lot more before you get out. Hell, be REALLY ecological, skip the tour and just check out the website.
Tres Rios is similar, and has more natural gifts. Three rivers come into the sea there, and it's full of cenotes and underground swims. They have jet ski tours, horseback riding, trained manatees doing soft shoe in top hat and tails.
There are lots of other such parks, such as Dolphin Discovery (Swim with dolphins! Live with dolphins! Get kinky with dolphins!) , Yalku (a smaller, out of the way non-commercial lagoon), Aktun Chen (caves), and they will be flogged on you everywhere. I'd say, try Xel-Ha and see what you think. Then try more if you have the taste and budget for it. Just don't tell me how freakin' ecological it all is. These parks probably appeal most either to people who can con themselves into thinking it's ecotourism or a wild adventure, or to those who don't give a damn and just want to do something bitchin' to kill a day. Or maybe to somebody like yourself, who can see what it is, and enjoy it for that.