Couldn't agree more with Dogle. From my experience on boats sea-sickness is psychologically controllable in the majority of cases. Those that start by convincing themselves they won't be sick are usually OK. Those that think they will/may be always are.
Having said that, at sea Stugeron is reckoned the most effective, the Navy should know, and that's what they use.
Available in any quantity
afaik.
ps. Vert rare to be seasick "all the while" Seasickness wears off after several (miserable) hours and rarely lasts more than 24, max 48hrs.
I think you'll find Nelson was sick every time he went to sea, which is very far from all the time he was at sea. That is not uncommon.
Not that 24hrs helps in the air. Take your stugies 2 hrs before getting airborne!