The best medications are available on script, these being Maxalon, Stemetil and Zofran. Zofran is used in chemo patients and is $$ the tried and true Stemetil is probably the best and most GPs would write a script. Make sure you take a dose 12-24hrs before you go out, do not wait until you get on the water or start to feel ill, it is not as effective.
J