Prepare for your trip well in advance, to help lower stress. Get plenty of sleep in the days before you leave.
Eat mild foods the day before leaving, nothing greasy or acidic, and eat sparingly. Drink water, milk and non-acidic juices before sailing. Do not drink caffeinated drinks, carbonated beverages or excessive alcohol before sailing. Take ginger capsules for three days in advance, 1 to 4 mg a day.
Arrive early at the dock and relax a while. Drink plenty of water, because dehydration can aggravate sea sickness. Focus on the relaxation and pleasure of the voyage to come.
Breathe fresh air out in the open; do not breathe engine fumes or stuffy cabin air. Relax in the shade, not in the hot sun.
Drink plenty of water and non-acidic fluids. Take ginger capsules with your drink, 1 to 4 mg per day. Take a sea sickness pill like Dramamine or Bonine if nauseated feelings begin. Use a non-drowsy formula, because sleepiness can worsen sea sickness. Eat a few peppermint candies. Nibble on soda crackers, which are good for absorbing excess acid in your stomach.
Gaze out over the horizon. Stay near the center of the ship, where you will feel less motion than at the periphery. Stay away from the higher decks, where the swaying motion is stronger.
Avoid people who are seasick, since it is strangely contagious, apparently a sympathetic reaction.
Sleep on your back at night. Keep busy and on your feet as much as possible during the day, because sitting down can make the problem worse.