I'm the same. I don't use gravol, it doesn't work well enough. I use Dramamine and seabands for flying and for cruising I use bonine, Dramamine and sea bands and am still sick. I'm going to try the patch next time I cruise.
Op: I definitely recommend getting seabands, they are inexpensive and do help. Also get bonine as recommended by others.
Sometimes with Bonine, I do feel a bit cloudy, but I guess that's better than the alternative.
I give my daughter a half the night before because we've found a couple of years ago, that she feels a ill during the first dinner. But after that she's fine. I always keep the second half in case she needs it, but she hasn't needed a second dose so far. I was going to try to just take a few in the beginning and see if I would be like her, but I'm just too nervous that I'll feel bad and ruin my experience. I don't take it for anything else and I love roller coasters, so I don't really get motion sickness anywhere else.