There WAS waterskiing at CSS last April...we went and had a blast. I am hoping they haven't discontinued that option. We'll be back home in 11 days to confirm. The evening entertainment at the Balloon bar is always a hot spot, but we're usually too tuckered out to join in.
Entertainment Must-Do's: Starlight Gala and Beach Buffet have music and entertainment(these are also your only options for dinner Friday and Tuesday nights, respectively), do Dunn's River Falls if you haven't gone before. Spend quality R&R time - find a hammock, float in the ocean, just chill out. I am always a go-go-go kind of person, so I have to put "do nothing" on my to-do list.
Take the time to look over the activities list when you arrive, go on the orientation tour (it helps you get your bearings when exploring the resort), and decide what you want to do from there. For water activities and scuba, you should go to watersports and sign-up sooner rather than later.
Hope this helps!