Seasickness is miseriable...planning ahead is always best. You were smart to try the meds before you sail. That's not the kind of drunk you look for on a cruise ha-ha!
You might want to try the SEA BANDS (WalMart or Drug store)
these are knit band to wear on you wrist...they have a small plastic button that places pressure on your wrist that help prevent sea sickness. NO MEDS...no after affects. They are not very expensive and if you don't need them you can return them when you get home. (if not opened)
They also work wonderfully for morning sickness in pregnancy. My DD has had 4 kiddos with extreme morning sickness until she puts on the bands