Where to dive into Mexico's underwater wonders

From an article by Christine DelSol on Seattlepi.com:

Mexico's Caribbean coast is as close to ideal for a scuba beginner as you can get. It flanks the Great Maya Reef chain, second-largest in the world after Australia's Great Barrier Reef. Capable dive instructors are as plentiful as iguanas, and when you break from the intricacies of nitrogen intake and pressure gauges, you have Maya ruins and friendly villages to explore, comfortable hotels and great restaurants at your disposal, and as much nightlife as you can handle. It may not be so for the skilled and slightly world-weary divers whose next stop is Thailand, Mauritius or the Red Sea, but for a beginner the right patch of terra firma is just as important as what's underwater. Open-water certification courses take four days, more of it on land than in the water.

Here are my best scuba spot candidates so far. Cancún dropped off the list early on; though its shallow reef and colorful marine life are certainly suited to beginners, the underwater scenery can't compare to nearby spots, and there are other places where I'd rather spend my time. Tulum was another early casualty, with a stunning reef just beyond its world-famous beaches, but dive operators who concentrate almost exclusively on cenote and cave diving, which is not for beginners. . . .