Good point. My first cruise we had really rough seas, and one of the entertainment staff told us it wasn't usually that bad. He said something like "This is the worst it's been in 6 months." This was back in 2007 on the Majesty of the Seas to the Bahamas (Royal Caribbean). That was on the first night, and on the second night, the captain kind of joked about it, asking "Anyone feel any motion on the ship last night?" We all screamed, "YES!" The captain just laughed, and promised us it would get smoother, which it did.
My last cruise we had choppy seas also between Grand Cayman and Cozumel. Like Penny, I don't usually get motion sickness, so I was fine.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)