I have been trying to book the CC Stingray Adventure online for the last month or so. I checked everyday and there was never availability.......... until today. So I just booked for our second CC day (we're on the May 27th Double Dip). I wonder if they release more times online as the cruise date approaches. Also today, availablity appeared for Palo High Tea.
So keep checking online and if you aren't successful before you cruise, hit the excursion desk ASAP after you board. Good luck.