Are you driving down? If so, I would stop at John Pennekamp State Park in Key Largo. They will take you 3-5 miles off shore to the protected reefs. Just gorgeous - lots of fish and corals. I was just there last month for the first time and will be back every time I visit South Florida. For $29.95, I think it is a great value. There is a $3 coupon available online if you take the early snorkel boat.