The key to sea sickness is go outside on deck and enjoy the rough weather and move around
Don't stay in the cabin away from Windows as sickness is thought to be a conflict between your brain receiving messages from your ears telling you you are rocking and rolling but from your eyes telling your brain everything is calm - which it will be if you are inside sat down
The sickness is a default of the human system which thinks it's being poisoned
So having sailed extensively on the Irish Sea with my father and have never been sea sick ever even on terrible cross channel crossings - always enjoy the fresh air and watch the waves and when inside move around - sleeping isn't a problem as you will have your eyes shut
Bon voyage
