I went solo to Chankanaab and quite enjoyed it. The snorkeling was perfectly adequate and quite close to shore, plus there are underwater statues, and they have a dive shop on site if you care to rent a tank. There are other things to do there too, like a sea lion show and tequila tasting and a walk with Mayan ruin replicas, but the beach area is gorgeous with shaded seats and hammocks. There were also free lockers available to use, which I found helpful as a solo. I would steer clear of the "with lunch" option, though. The lunch is served at one buffet, and the lines are so long they spiral inside and out of the building, and it's not even good. There are 3rd party restaurants on-site that offer a better value. That said, as a solo, I've found that the price of the excursion through the ship is approximately the same price as going independently, and if I can get a free drink at least...Hey! Bonus!