I'm a seasoned traveler, former deckhand, and a budding reference librarian, all qualities that uniquely situate me to answer your question. When I was working as a deckhand in Alaska I battled seasickness everyday. I found these things helpful:
- sit or stand near the rear (stern) of the vessel
- sit near a source of fresh air
- face forward
- rest your head against the seat back while focusing on the horizon
- avoid greasy, rich foods for 24 hours before the boat ride
The Mayo Clinic also recommends abstaining from smoking cigarettes and cigarette smoke. Here's a link to their page on motion sickness:
Also, in my experience, riding on a multihulled vessel, like a catamaran, greatly reduces the likelihood of seasickness as multihulled vessels do not roll side-to-side in the water as much as monohulled vessels.
If your wife begins to feel sick, she might try some breathing exercises, such as regulating her breath by slowly counting while remaining still and continuing to face forward. I have also found ginger to be a very effective homeopathic remedy for motion sickness. Visit the National Center for Complementary and Alternative Medicine(NCCAM )website for more information on the use of ginger to prevent/treat motion-related sickness. Here's the link:
If your wife must resort to medication I'd recommend Bonine brand. I took it several times on days when the sea was extra choppy and it did the trick. However, she must be sure to take the medication at least an hour prior to boarding the vessel. I switched to Bonine from Dramamine because it doesn't cause as much drowsiness. Per the travel website Lonelyplanet, Bonine is available in Israel.