My sister-in-law has also used them while on a cruise of the Caribbean. She took Dramamine with her, but opted for trying the Sea Bands first. She said they worked for her and brought home all of the Dramamine she had taken with her.
They don't work for everyone, but I have had good success with them. A fellow diver offered the use of hers so I could continue diving one day (I was her dive buddy and she would have been stuck on the boat otherwise.) They worked so well that I bought my own pair as soon as I got back home. I take them on every trip.