Before boarding any boat (big or small) try to avoid consuming things that are likely to make your seasickness and nausea worse, such as alcohol, caffeine, fatty foods and spicy foods. Heavy, greasy meals contribute to the development of nausea, which will be worsened by the motion on the water. That being said, it’s important not to travel/sail on an empty stomach either. Focus on drinking lots of purified water and eating small portions of low-fat, high-protein foods such as grilled turkey or chicken breast, lean fish, cottage cheese, or legumes.
When booking travel on a cruise ship or boarding any other decent sized boat, try to get a berth or seat as close to the center point of the vessel as possible, because that area will experience the least amount of motion. Also try to get as close to the water as possible because the further away you get from the surface (the top decks of cruise ships, for example), the more motion you’ll experience. In addition, try to seat yourself facing the direction of travel because you’ll feel better orientated.