gregor1234:The site below lists several excellent shore dives for Grand Cayman. We went to GC last summer and shore-dove almost every day. I would strongly advise renting a car and driving to dive sites on all island coasts.
http://caymanislandsdiscounts.com/offshore_diving.htm
Also, follow the off shore snorkeling link on the site above to find top shore shorkeling sites on GC. Some dive shops will not rent tanks for shore diving so call around. We stayed at the Tortuga Club on the East End and enjoyed the excellent shorkling right off the beach there day and night.
You can also dive off the dock at Sunset House, but you must use their tanks. The main attraction is Amphitrite, the tall bronze mermaid statue buried in shallow water near their dock.
www.sunsethouse.com