I get sea-sick cruising, even on short daysails, but never while
racing. I think this is because I am concentrating on tactics, maneuvers, other competitors, etc.
I can confirm that singing out loud works in preventing sickness, especially if you are joining in a sing-song, and have to listen to the main singer for most of the song. I think it's for the same reason, that the brain is concentrated on another task and distracted from signals that are causing the motion sickness.
I take Stugeron the night before a
cruise and the day of the
cruise. It does the trick.