The attractions are the amazingly clear and warm waters, the famous Jellyfish Lake where one can swim with non-stinging golden jellyfish, the large numbers of big manta rays, many sharks, large fish, WW II wrecks, vibrant reefs and the beautiful Rock Islands. In addition the side trip to Yap featured even clearer water and a native life that wasn't changed much by WW II. Recall that Yap is the place famous for the circular stone money.
The water was so clear at times it felt more like flying than diving, freaky clear especially off Yap. I wish I had good pictures of that, but my point-n-shoot isn't good to diving depths, so I only have a few pics on land. There isn't much to do in these places outside of diving or touring the famous Peleliu island, where an especially viscous battle was fought during WW II. We did not visit as a recent typhoon had impacted that island and disrupted services.
Anyway a few pics I have can be found here: