We did not notice much movement of the ship. The ship has stbilizers that limit the amount of movement that is felt. After a day or so, you do not notice much.
The only time that we noticed anything was when the ship had to stop in the middle of the ocean (Western Magic 7 day Cruise) to assist some refugees from Cuba on a small little raft...yes true story, right at the second dinner session. It then had to make up time, so was traveling at a higher than normal rate than at any other time of the cruise. That was really the only time that we "felt" the ship moving through the water.