All three shops in Akumal are reputable - Akumal Dive Shop, Akumal Dive Center and Akumal Dive Adventures. Each has their following but all are good, just slightly different atmosphere.
I've been going to Akumal once or twice a year for about 5 years. We rent a condo in Half Moon Bay and do our ocean dives with Dive Adventures. We use Dennis Weeks (Diablo Divers) for the cenotes. The ocean diving is very easy drift diving in a light current. The reefs are pretty healthy and good marine life, considering it's not a protected marine park. You won't find the color you get in Coz, but they are pretty lush with lots of soft stuff. I've found that marine life is a more abundant in the winter and early spring then summer. They did suffer some bleaching last summer with the higher water temps and less rain (aside form the hurricanes). You will see spotty sections on some reefs while others are fine. Some of the majestic, huge elkhorn did get damaged from Emily, which was sad.
My favorite dive trips are to go to Cozumel for a few days then to Akumal. Very different diving in both places and totally different top side as well.
