After watching two regular UK buddies - Davey Willo and H - pebble-dash the port and starboards of particualr dive boats (or be VERY close to doing so
), and having had to transfer my wife onto a relief boat to take her back to shore at Aliwal Shoal, South Africa, so we could strike out through the swell and surge to dive, I can recommend (not that I have ever been seasick and have never taken it) Sturgeron!! My wife swears by it.
If you can catch Howard, ClaireDJ or Spike on a return trip from SA, ask them to snag you a couple of boxes!! The UK boxes are sold with 15 mg tabs - the SA boxes are sold in 25 mgs tabs!