Usually, I'm not eager to go on a cruise, as I might get sea sick . While on a bus or train I refrain from reading, as I might get a feeling of nausea or even dizziness.
Below is a picture taken years ago with me (covered head) and a friend, on a ferry voyage along the British channel from Dover to Callais. I had a terrible nausea followed by loss of colour in my face.
I've never attempted to get to the bottom of 'motion sickness' or take medicines. I 've just accepted the situation. When feeling unwell, I help myself with doing what seems the right thing to do. On a boat , I'l go to the deck for fresh air and look forward in the distance. On the bus, I'll look straight ahead or out of the window. A bottle of cold soda water may also prevent or reduce nausea.
I notice , in my case, that with age, there's significant decline in motion sickness, and that makes me glad, of course. Several years ago I went on a boat tour along the river Moskva in Moscow. Had no trouble at all.
Recently, I 've incidentally come upon an article on the above subject by James Phillips, a researcher from Washington University. He explains 'motion sickness' as a conflict between senses (visual sense of the eyes, and audial sense of the inner ear) that interferes with the brain's processing of the moving information. He calls it 'mismatch'.
As a college student he experienced seasickness ; that made him decide to search it thoroughly and may be find proper treatment someday.
In the meantime, people use a variety of more or less efficient means for preventing or stopping motion sickness, such as accupuncture wrist bands, skin patches behind the ear, herbs like ginger and chamomille, aromatherapy etc...