Get plenty of sleep the night before you will be on a boat. Avoid drinking large amounts of alcohol, and don't eat greasy or acidic foods. Don't read while you are on a boat, and avoid other people who are seasick.
Antihistamines, including Bonine (meclizine), Dramamine (dimenhydrinate) and Benadryl (diphenhydramine) are often used to treat seasickness. However, these drugs often cause drowsiness as a side effect.
Phernegan and Transderm Scop are two prescription drugs for seasickness. Phernergan (promethazine) is an antiemetic pill; Transderm Scop (scopolamine) includes a pill and skin patch that is worn behind the ear.
Ginger and peppermint are often used as natural remedies for seasickness. A 2000 University of Exeter review of clinical studies reported that 1 gram of ginger can be helpful in reducing nausea.
Acupressure wristbands may prevent or reduce nausea. Standing up and looking at the horizon may also help. Placing your feet in ice water has also been reported to reduce nausea.