There is an old recipe against motion sickness:
Brace a big 200 years old oak tree with both hands :-)))
In fact any tree will do, as long it is hard on the ground.
OK, to be more serious:
To me and my wife ginger works, but we are not usually sea sick.
Ginger does not work for all people.
Once I did have some problems. I was disassembling and reassembling the clogged toilett underway. Big swells, being down below, bad smell and being bent over in an uneasy possition almost had me "use" that tiolet before it was fixed. :-)
A method I use when I am inside (and it helps me a lot) is to close my eyes for a few seconds. This brings short term relieve, so you can continue wour work below. But then I need to go out on fresh air.
What we usualy have on board is Dramina, but it knocks people down.
So we usually have half of the crew being "passangers", sleeping a lot.
I only sailed short distance sailing (up to 60 or 80 n. miles in one passage), just a few overnight - so I yet have to discover what it looks like when things are really bad - and for a long time...
Hope ginger will help then.
So things which worked for us (not to all and not always):
- Get behind the steering wheel and handstear the boat - rated number one remedy.
- Do not go down, stay on fresh breeze and look at the horizon. If you do not feel good and feel a bit cold: ask for more cloths to be brought to you, do not be a hero and go below to take it. Dress more immidiately when you feel cold, not when you are already blue and all stiff and sick. A real hero for me is the one who admit he is not feeling good, not the one suffering until it is too late.
In most cases I have seen: when it gets you there is no way out (except to the oak tree).