Hi,
I have dived on the East End of Grand Cayman, which many people have told me has the better diving than the Seven Mile Beach area on the west side of the island. I thought that the diving there was great, very comparable to what I saw in Little Cayman, which is one of my favorite spots in the Caribbean. Also, this side of the island gets none of the cruise ship traffic, or car traffic, both of which can be problematic on the west side.
The thing that I liked about the diving was that there was lots of interesting underwater topography and swim throughs. Here are are a couple of examples.


The reefs and fish were both in good shape when I was there a couple of years ago. I would like to return when I get the chance.
Actually, Ocean Frontiers (mentioned by Giles) was the dive operation that I used, and they are on-site at the Compass Point Condominiums, which are very nice. It is not a fancy resort, but it is comfortable and extremely convenient. You just roll out of bed, and walk to the boat and dive. There are several restaurants within a 3 or 4 mile radius, so we usually ate dinners out. There is a grocery store about a mile or two north of the Compass Point resort where we stocked up on breakfast and some lunch supplies. I thought that the dive operation at Ocean Frontiers was first-rate, too. There were good dive guides, and the boats and equipment were fine.
The only caveat is that the seas can be a little rough during winter on the east side of Grand Cayman. However, you are probably safe going in March. Others might have more information on that. (We went in early summer, which was fine.)
I hope that this helps.
-Erwin