After a rough first night on our first cruise, we do the half-tablet of Bonine before boarding and sometimes on the second day. But we don't need it after that.
Another thing I have found, which sounds really strange, is that if you start playing the VR (like the Oculus Quest), your inclination to get motion sickness decreases significantly. Your body adjusts to the motion sickness caused in VR the more you play, and that translates to real world experiences for me. I didn't even need Bonine on our last cruise and rides that used to get to me at theme parks don't even phase me now. It's pretty great. Odd, I know.