There are a few things that make sea sickness worse
Hangovers, Tiredness, Alcohol, Fizzy drinks, overheating and staring at the bottom of a rocking boat.
and a few to make it better.
avoid alcohol before and during, try to sleep well prior, drink water/tea, stay in the fresh air looking at the horizon and stay busy.
But the one that worked best for Dan, [who suffered regularly when young] was snacking on ginger biscuits
He has not been sick for years, but still enjoys a ginger nut onboard