Akumal is a great place for scuba divers, swimmers and snorkellers because it's on the Mesoamerican reef and Yucutan cave system. There are amazing ocean dive sites 5 minutes from shore, plus there are many cenotes nearby that you can swim, snorkel and scuba dive in as well. Akumal is a very safe community that is lively with lots of great restaurants, but also offers some peace and quiet that you don't get in the more heavily populated nearby downtown Tulum or Playa Del Carmen areas. I like it here because it has some great restaurants and lively bars but is also very laid back and relaxing and does not feel touristy. The bay does not allow boats and so it is very private. It is shallow for swimming and always warm.
Check out www.lolkanaab.com where I describe the property in area in great detail.