I recall 2 notable dives of the south coast of Cuba. The most famous would be the Colon wreck, which is a couple hours east of Santiago (the road it in very poor shape due to hurricane damage). This is a shore dive, with the wreck being about 100 yards off the coast. It's a very rocky entry, sometimes with big surf.
The wreck sits in about 90 feet of water (iirc). I don't recall the history of the ship, but you can look it up on the web. There are dive centers at Marea De Portillo and Brisas Sierra Mar. It's hit and miss when and if they do this dive and there is always a cab fare involved. I think the cost was about $90 CUC a few years back.
The better dive (IMHO) is "The Ferry", which is east of Santiago De Cuba. It's an old car ferry (approximately 100 feet long), which lies upside down in 125ft of water, right on the edge of the wall (drops to 5000 meters)
The great thing about this dive is that the middle deck of the ferry is wide open making it easy and safe to penetrate. When you emerge on the south side of the ferry, there is a very narrow ledge (about 2 feet) and then the drop off.
It's really quite a spectacular dive.
There is also good diving to be had along the north coast. If you're in the area of Santa Lucia, there are many good reefs and also a shark dive. Shark Friends dive center is located amongst the many resorts in the area.