*Well, at least for me anyway. Each person is different!
As far as getting nauseous easily I think I must be one of the worst travelers/wanderers out there! The very first thing I do when I get on a plane is discretely check my seat pocket and my neighbors-just in case!
As I write this I am sitting on a sailboat, have been on rough-ish waters and have been fine-no problems whatsoever (still crossing my fingers!)
And I have to give major thanks to the crew of Norwegian Jade, particularly my cabin steward Floyd, for these best tips that work. On a 16 day repositioning cruise crossing the Atlantic we had some rough seas and I did not get sick!!!:
In order of importance:
*1. Eat green apple (granny smith). Apparently there is something in the pectin (so eat the skin too) that interacts with the acid in your stomach. To keep you from getting nauseous. I don’t need a lot of apple I just try to keep some (½ or ¼ apple ready to eat and in my tummy).
*2. Don’t have much liquid in your stomach. This makes sense to me. Then there is less to slosh around. I don’t know why I didn’t think of this myself.
*3. Eat salt. Eat saltines or I have Himalayan pink salt in a grinder that travels with me. I eat that.
*4. Eat normally (using some common sense of course). I do better if I keep something in my stomach.
Other things I do:
5. Eat ginger. You can swallow it whole. I like the pieces that are coated in sugar that are usually near the produce department (of course I do!)
6. Wear acupressure sea sickness bracelets. I think these help a lot.
7. Face it! Face forward not sideways or backwards. Don’t read, look down, or be on any devices.
8. Stay cool. Keep the temperature cooler rather than warmer. Wear layers.
9. Chew cumin seeds! Really!
It’s hard for me to say exactly which ones have always worked for me as I have not done just one but employ several methods at the same time. Mostly I rely on the first 3 but when I ran out of green apples recently (in the middle of the ocean in a sailboat) I focused more on ginger and cumin seeds!
I wish I had known these hacks when my daughters were little! It sure would have saved a lot of misery. I hope these hacks help you. And of course my disclaimer is I am not a doctor, just someone without access to regular medical care who has figured out how to McGyver herself together!
My Life as a Tumbleweed 
Those are all great to know. Never knew about the cumin seeds. Yummy.
Hope they help! They sure have been a game changer for me!