For travel sickness generally, try using the 'Sea Bands' - available from bigger pharmacies whose name begins with 'B' and ends in 'S' and rhymes with 'loots' [hope this doesn't count as advertising,
L]
The tablets which are claimed to be very effective and non-drowsy are Stugeron (when I worked on sea trials, many of the guys I worked with used these and found that they worked), but I would strongly recommend trying all the non-pharmaceutical options suggested so far before resorting to drugs.