FYI, you will feel the least amount of motion on the lowest passenger deck at mid-ship.
Here's my remedy for sea sickness: eat apples and crackers together, do not drink anything, do not lie down. Go outside (if possible) and look at the horizon. A ship's officer suggested this and it worked like a charm.
Also, take Bonine a day BEFORE the cruise, and then follow the directions. It doesn't work once you're sick.