Akumal is beautiful. Make sure you snorkel there as well as dive. There's really good snorkeling just a few feet off the beach. If you like turtles, you'll be in heaven. Specifically, right in front of the Lol Ha restaurant out over the sea grass patch is prime turtle spotting territory. I have seen so many on some snorkels that I quit counting. You'll also see rays, BIG barracuda, and lots of the usual tropical fish, but the turtles are the best part IMO. If you're staying in Akumal and you're into it, do a turtle walk with the CEA at night. We saw a huge loggerhead turtle come up on the beach, make her nest, and lay her eggs. It's a truly unique experience. Try Lucys shrimp tacos (she's in town behind the supermarket), and home made ice cream. Make sure you do some cenote dives (with Dennis from Diablo Divers/Aquanauts). Check out locogringo.com for a ton of info about the area.