I had to admit that boat diving was going to be much more fun without worrying about seasickness. I've used OTC products very successfully (Bonine, etc) for day trips, two-tank dives, whale watching. For overnights/liveaboards I've now started using prescription patches, good for 3 days, and have had absolutely no problems. The overnight thing was very risky for me until I used these. Ask your doctor for scopolamine.