Brain expects movement (from visual stimuli) and doesn't feel any movement? Nausea. (VR sickness)
Brain expects stability (from visual stimuli) and feels movement? Nausea. (Sea sickness).
This is why when you're sea sick they tell you to watch the horizon, because if you watch the horizon, you can tell that the horizon is going up and down and your brain can correlate that to the motion.
Brain expects movement (from visual stimuli) and doesn't feel any movement? Nausea. (VR sickness)
Brain expects stability (from visual stimuli) and feels movement? Nausea. (Sea sickness).
This is why when you're sea sick they tell you to watch the horizon, because if you watch the horizon, you can tell that the horizon is going up and down and your brain can correlate that to the motion.