Carriacou & The Grenadines. North of Grenada there are some little, laid back islands with gorgeous beaches and beautiful reefs. Especially the Tobago Cays are very famous because of their extended reefs, where you will find lots of Hawksbill turtles, who are grazing from the seaweeds. It is also the home of the nurse shark and an innumerous amount of tropical fishes. The waters are so clear that all the bright colors of the reefs and its inhabitants nearly blind your eyes!
More info:
http://en.wikipedia.org/wiki/Tobago_Cays
http://www.turtles.org/hawksd.htm