For something completely different, check out this far-flung resort situated within the Bacalar Chico Marine Reserve. It's nothing too fancy, and there's nobody for miles, but the point is that you can walk a couple of hundred feet from your cabaña, strap on a mask and snorkel, and boom, there's the reef. It's ideal for families seeking a low-key vacay.
Accommodations include fully-equipped one- and two-bedroom cabañas, a budget suite and a 'prime minister's suite,' which is gargantuan, with a great upstairs terrace. The Aquarium seafood restaurant is on stilts over the water, where eagle rays, tarpon and bonefish tend to hang out at night. (This is an ideal time to snorkel.)
It's possible to get here on a golf cart, but it takes around two hours from San Pedro, and much of the trip is on the sand. A ferry transports most guests to and from San Pedro, and will bring day-trippers for around BZ$30 each way.