We were there a little over two weeks ago during WONDER's repositioning to New Orleans. The usable beach is very short from the waterline back towards the cabanas. There is a big jump up to where the cabanas are from erosion. In-water is not too changed. Thecwater depth for some reason has trended shallower and shallower for years. You can go quite far out and still be barely waist high. The bottom itself hasn't changed much. The further away from the arrival area, bar and restrooms, the less rocky it is.
As to crowds, we arrived there later since we wanted to explore the family areas, plus due to dietary needs had to pre-arrange food, which they prefer to do at Cookie's. So it was near 1:000 by the time we arrived at Serenity Bay. No trouble finding loungers and chairs, but people weren't as spread out as in the past.
One disturbing aspect was a couple nearby who had brought a small, maybe 12 inch cube, boombox on which they had music that was clearly heard for dozens of yards around. We had been pretty far out in the water, but it was going when we came back to our chairs. Folks next to us said it had been going for quite a while. By that time, it was nearing departure time, and they packed up and walked off before the lifeguards walked along stacking the loungers. I would have notified a lifequard or other castmember otherwise. It was the first time we had ever experienced that. I always credited
DCL for not even piping in their own low-key soundtrack to that area.