My husband and I only take day trips on boats due to his propensity to motion sickness. He loves boating and snorkeling, but unfortunately gets seasick, especially when there are swells. The solution he uses on planes, boats and after snorkeling is a device called the "Motion Sickness Relief Band". It can be found online at Hammacher Schlemmer, probably Amazon too. It is the only thing that works within minutes of him feeling icky. Below is a description of how it works (electrostatic pulses.). Please note it is splash-proof but NOT water proof and you can't wear it in the water. My husband wears it on the boat when we are under way, but sits where its unlikely he will be splashed. I tried it once when I was ill and so nauseous I wasn't able to move an inch without being sick. It was amazing how within minutes it "broke" the sick feeling. The wrist bands using acupressure don't work for him. The patch works but makes him so sleepy. Also note that you need the conductive gel to make it work, so we travel with extra batteries and gel.

Employing a treatment proven effective in multiple medical journals, the band transmits gentle electrostatic pulses to the wrist’s P6 acupressure point, harmlessly disrupting the nerve signals between the brain and stomach that cause nausea. The reusable device does not require abstaining from food or drink and quickly alleviates symptoms without causing drowsiness.