Preventing motion sickness during a marathon swim

Several years ago when I started training for a marathon swim in the ocean, I experienced motion sickness (dizziness, nausea) from the swells. I was surprised because I thought that would happen to the boat crew not a swimmer. I was ill-prepared so I stopped my swim. Determined, I returned the following day with some over-the-counter medication (Dramamine). And I was stunned to experience the same ill effect after swimming in swells for a couple of hours. But I soon discovered some helpful remedies from other marathon swimmers. While swimming, look at land. If land is not visible, look at a cloud. Try to avoid looking at a rocking boat. If your boat is guiding you, than briefly glance at it every 15 to 20 strokes. Wear ear plugs--- this prevent water from moving back and forth on your eardrum (it works). Practice dry land exercises for balance--- close your eyes during these drills. Also, train in rough water conditions --you will become acclimated to swells. Just like your body becomes acclimated to cold water temperatures, it will acclimate to swells.