Have you tried doing a search on Grand Cayman? Try this website www.caymanislanddiscounts.com. Click on "Home" then "Offshore snorkeling". It should work. This site has a map and gives details on many of the snorkeling sites along with directions, water depth, entrance difficulty. I used it before we went this past March. I printed it out so that I would not get lost finding a site.
The Cali is a walk to the left after getting off the pier. At the pier there is a small tourist booth. You can pick up a pocket guide to Cayman. It has a map of the island and shows all the diving and snorkeling spots to go.