Everyone's different. I've seen people flattened for a couple of days taking over the counter stuff like Stugeron and Qwells, so if it's a short haul I wouldn't bother at all, it stops when you get off.
Speaking as someone who's - so far- always very seasick after 24 hours in, I'd go with Buenchico and say ginger in some form of either fruit, biscuits or ginger beer, plus plenty of water and salty snacks like crisps and pretzels. Put up with it, sleep when you're not being sick and look forward to scarfing a large, very restorative fry up as soon as you can.