From my experience at sea (well away from land and lights) on a dark night. This doesn't affect everybody. It doesn't happen to me...BUT..some people are affected by loss of visual orientation ...boat rockin and rollin combined with the loss of a
Visible Horizon.......resulting in Sea Sickness. Thats puking.
It has something to do with the inner ear..equalibrium..lack of a visual horizon combination. I can't explain the particulars.
I have seen Macho guys turn to MUSH under these conditions.
My Advice: Do NOT go down into the cabin..night or day..if you feel sea sick. Stay OUT in the cockpit with fresh air and a visual horizon.
NB