I have the sea bands but never found them to work for me. I take ginger tea (capsuls with ground ginger that you can put in hot water). What works best for me is Bonine. I take it once a day (chewable) starting the day before we board. Even if feeling fine, I just go ahead and take it each day till we're off.
DW uses ginger for airsickness. It works well for her. You can buy it at Henry's market or any health food store. It may be bought at your local supermarket (Ralphs) also. DW likes to buy hers from Henrys market because it's organic.
You can buy ginger in capsules - much easier than making tea or transporting candy. It works quite well, but if you are really prone to motion sickness I would suggest using it in addition to Bonine or Dramamine II, at least until you know how the seas will be running.
A friend of mine brings along the ginger candies. She didn't think the bands worked. On one ferry ride back to St Maarten from St Bart's I actually needed one and it really helped. She gets the chewy kind and they're available in most markets. I think she gets hers in a natural food store.
the ginger works great for the mild queezies, candy form, cookie form or in soda-only if there is really ginger in it, and not just flavor. Its the remedy that you need to take at the first sign of those queezies. The seabands work very well also.