I would like to add my two cents in on this but not because of my experience in diving or having a degree, but as a gamer.(laugh all you want but hear me out)
A bit of context...
A few years ago, a new device was emerging that would be a game changer for the world. It promised not only a new gaming experience but a new way of learning and communicating with others. This device was called, the Oculus Rift. It was the first of true real time virtual reality at home.
Fast forward to right after I got mine and a few months later when I got the motion controls. There was a problem when you did certain movements where your sensory input did not match what your vestibular system (balance and weight distribution) was telling your brain. This, in the gaming community, was known as hurling because it was so strong in some people that they would literally vomit the moment they realized something was off.
The term "getting your VR legs" came about because if you pushed through it slowly and worked on it,just like aiming a virtual sword to hit a virtual enemy, it got better. The main source of sickness was strafing (moving left or right while facing forward). In gaming,this is necessary but in real life,you just don't move like that.
In other things,like a rollercoaster, you can feel your stomach drop even though you are sitting in a motionless chair, so VR was fully tricking the vestibular system, including your sense of gravity.
After I got my VR legs, I have never been seasick again, with one caveat, I have to have food in my stomach before. How did I get over the sickness? Ginger gum or a peppermint candy. I tried other gums and other candies,but ginger gum or peppermint candy worked to settle my stomach until I was able to push through it.
Now, when I know I am going to be on a boat or in a situation that I would normally have gotten queasy, I remember to "disconnect" and while I have not been through any scientific studies or specific tests, I know that I won't have that issue, at least for the situations I have been in this far.
I know it's all conjecture and circumstantial evidence, but I really do believe that we can train our brain to allow for mismatched inputs.