It's been about four years since we visited and we weren't camping at the time - so can't speak to campground water. But can speak to things to do....
Definitely take time to tour Atalaya Castle and Brookgreen Gardens across the highway from the park.
There was an incredibly nice Nature Center. They had a pretty destructive fire a couple years back, so don't know if that's been rebuilt or not.
But always keep your camera handy! Wildlife everywhere.
See here for a snapshot of our visit: Picture a Different Myrtle Beach – Picture The South