Sea Sickness is very much related to hydration. Stay well hydrated the few days before your charter. Also, try to avoid alcohol if you can in the couple days ahead of time and don't start with an empty stomach. Other than that, in addition to the over the counter remedies above, ginger is a great natural treatment. We are big fans of scopalamine patches, which you will need to get from your doctor. Make sure to place this 24 hours prior to departure and change it every 72 hours. Spend as little time below as possible at least while you are acclimating. July will be hot, so consider A/C on your charter, if possible.