I've found that ginger tablets or apples do wonders to cure seasickness. You can buy ginger tablets at a drug/vitamin store. The apple cure is easiest as all you have to do is run up to the buffet. Best yet, it's free and has no side effects.
While the weather will be warm outside in February, the air conditioning on the ship may be turned high enough to require a sweater or wrap while on the ship. Also remember to pack some clothing for evenings onboard.