Antihistamines. For sea sickness: dramamine (dimenhydrinate) is the most commonly used one. Other are Diphenhydramine (benadryl) and meclizine. In order to prevent sea sickness you need to take them before you start feeling sick, preferably before you get on a boat. Meclizine has less of a drowsiness effect, the rest may make you drowsy.
Non-med options. I agree with dr. Peck. Here are some non-medicinal remedies: acupressure, sea-bands and ginger or peppermint tea.