@KathyV - great job as usual in providing great info about different areas of the island(s).
The time of year may make a difference. Have been on the East End in summer and winter. When we were there in June of 2010, snorkeling at the pier of Morritt's Tortuga Club was my first close up encounter with a reef shark - tropical fish were around, probably due to the fact there is a restaurant on their pier. My wife and I used info I'd found about entry points for shore dives, found an off road area we could park along the north coast, and found a large beach area that we snorkeled in several places (saw some cuttlefish or squid amongst other things) - it wasn't great snorkeling but we didn't go very far out. Starfish Point beach (near Rum Point) is a unique place to snorkel if visibility is good. Haven't snorkeled at Rum Point, but have heard there were some decent places, such as Cayman Kai Beach, around there. Rum Point is also close to the bioluminescent bay - not sure if you can find an entry spot on your own and snorkel in or if it's regulated in some way for tours only, which is how we did it. Was in GC just a few winters ago (staying at Compass Point) and didn't attempt any snorkeling in the ocean (except for in bioluminescent bay and at the Turtle Farm lagoon the prior week) as the diving was rough enough! Enough about snorkeling on the East End.
If you were on the East End for the week, things to do include Crystal Caves, the botanical garden, Kaibo Beach Bar BBQ on Tuesday, Stingray City from Kaibo Beach or Rum Point, and sightseeing (blowholes, ten sails, Mastic Trail hiking.) A day to go into Georgetown or a ferry from Kaibo Beach to Camana Bay for shopping/dining is also an option. Plenty of restaurants on the East End, including 2 favorites - Big Tree BBQ and Kurt's Corner on Frank Sound Rd (between Crystal Caves and the botanical garden). We're going back to stay at Morritt's in April and I'm hoping the daily specials at Kurt's are as good as a few years ago!
Not trying to sell it (just sharing info), but just saying a person could stay busy for a week on the East End, especially if you add diving to the mix.
Compass Point and Ocean Frontiers (pretty much the same people) will be one of the best diving experiences you have as long as it's not winter - they will take care of your gear (if you have your own) from the moment you arrive from carrying it from your room when you arrive to having it dry and back at your room before you leave. They have a schedule for the week of dives that they do. Lot's of friendly, knowledgeable staff.They have an instructional pool, as well as a separate pool with a hot tub. The restaurant is pretty good also. It is iron shore, but they have a sandy area to sit, relax, and watch the dive boats leave and come back - if you're not on it.
We booked through, I think, hotel.com (it's in a trip report somewhere here on SB.) Compared to Compass Point's online deal, even with rental car and diving, we did better piecing it together ourselves.
Bottomline - you'll like wherever you wind up!