Being in a lecturing room is much easier than being on a rocking vessel. Out at sea, in a storm that changes the color of your face, you can easily forget all the wisdom you gathered in the temple of knowledge. Instead of taking samples of seawater, they are now donating liquids to the ocean. Whoever tells you that they have never been seasick before, was either not on the right ship, or on the right ocean, or comes from another planet. One voyage you make without a single burp or fart, the next one your stuck with a bunch of sick souls.
Some people are more prone to seasickness.
It sticks between your ears, but you feel it in your stomach. The balance center of the inner ear tells your brain the body is moving, but the eyes tell the brain it's not. These different messages can cause symptoms such as dizziness, fatigue, nausea and the tendency to vomit. It doesn't stay with tendency. Especially after having enjoyed a gastronomical feast of champagne, BBQ ribs, sausages and burgers.