My wife and I just returned yesterday from 10 days at Sandals Regency. Due to the final stages of a cold, we didn't dive for the first few days, but then went daily. The Regency and Halcyon use the same dive facility, while the Grande Lucian has its own, but both go to the same dive sites.
Every morning there's a two-tank dive in the Anse Le Raye / Anse de Chastanet / Soufriere area, including wreck dives, wall dives, drift dives and reef dives. Typically, the first dive was in the 60' range for 45 minutes or so, followed by a SIT of 45-60 minutes and a second dive in the 45' range for 40 - 50 minutes. Times varied with the air consumption of the group's biggest breather.
Although not as rich as, say, Bonaire, the reefs still had a good amount and variety of coral, sponges, fish and other creatures. I'm not sure that I would go for a dive holiday, but I would most certainly plan on diving if I was headed there on holiday. I took all of my equipment, while my wife took only her mask, snorkel, reg, computer and skin. I had a 3/2 wetsuit but never wore it, sticking to swimsuit and snorkeling shirt as the water last week was consistently 81* - 82*F. Sandals provides all basic equipment, so you don't have to take anything with you should you choose not to.
The dive boats are Newton 46's, and with only small numbers of divers each morning, there was tons of space. The vast majority of divers were experienced, although there were a couple of days when newer divers were along for the dive.
The DM's and boat captains were excellent, both very knowledgeable and helpful. While Sandals insists on guided group dives, the small numbers and positive attitude of the DM's kept the dives enjoyable. The crew members were some of the best I've dived with.
Everyone must do an afternoon check out dive before doing the morning dives. The check out dives are short (30 min max) and shallow.
Hope that helps give you some idea of what to expect. Bottom line is that you should certainly plan to do some dives. You won't regret it.