My wife and I have been going to Grand Lido Negril's sister resort, Grand Lido Braco for the past 4 years - and love it. The Grand Lido resorts are very plush and the staffs are fantastic. Diving in much of Jamaica will not provide a great deal of fish life - it is basically a poor country and the natives fish it hard for food and in the process a lot of coral is destroyed by the traps. The water quality is great, with visibility ranging from 50 feet to over 100. The water around Negril, on the west end of the island, is fairly calm and not too deep, so the diving is easy. GLB is located on the north shore, so water tends to be rougher and afternoon dives are rare because of the winds. However, the Cayman trench comes close to shore there and it is far enough away from the cruise ship ports and larger cities that the area is much more pristine. The wall dives there rival those off Grand Cayman's north wall - and there is no shortage of sealife. I would agree that much of Jamaica only has fair diving (but can any diving done in warm clear water be bad??) - but there are places where it is outstanding.
If you go to GLN - you will be pampered - that I do know!!