What causes sea sickness really?
It is because the fluid in your ear says you are moving (this is particularly acute on the sea, as you are moving up and down as well as forwards) wheras your eyes say you aren’t. If you are inside on a boat then as far as your eyes are concerned you are sitting still in a room – but your inner ear says you are rolling up and down. This is made worse if the room is moving differently to how the fluid is moving – if you are rolling about the fluid will continue to move in one direction whilst your eyes see you’re moving in another. This is why reading makes it worse and looking at the horizon (meaning the discrepency is lessened as your eyes can see you’re moving, and has a standard reference point) makes it better. Seasickness can also be made worse by the movement of the bowels against the diaphragm, and even by psychological affects – some people get seasick from setting foot on a ship, even if it is in a dry dock.
