My husband and I did this when we were on a Celebrity cruise. We booked it independently (they have a web site, I think).
DH LOVED it, and I liked it a lot. It was very fast (for him), but felt pretty safe (for me). I did fall off the seat onto the back of the rhino and gave my tailbone a good crack. I felt that for days, let me tell you...
Make sure to have your sunglasses on a string--those things do move!