|Subject: Re: Cozumel|
A few years back we spent a week at Tankah Bay which is just a few miles north of Tulum. It has all the features you're seeking; huge lagoon with a barrier reef about a half mile offshore with excellent snorkeling, just a couple of miles from the ruins at Tulum, and a variety of accomodations ranging from hotel rooms to rental homes. Here are a few sites about accomodations in the area.
Also, message #29670 in the archives (Subject heading Playacar), dated Sept. 21, 2003 has some information regarding activities in the area.
John in San Diego