Opt for simple foods like toast, fruit and juice. Pop a pill. Common brand names include Dramamine, Bonine, Marezine and the Scopolamine patch. They work, but almost all cause significant drowsiness. This makes them fine for the flight down to Roatan or the 30-hour crossing to Cocos, but they should be used with caution on the day of diving.
Medications work best when taken before travel starts.
Follow the instructions on the label. If you feel like eating, stick to bland foods like plain crackers and dry toast. Although you may have already become nauseated, medications such as Bonine and Marezine can reduce your symptoms. Here's basic first aid for the most common diving scrapes. The key to avoiding all these problems is a respect for the ocean environment.