Living on an island for as long as I have (and working on a commercial fishing boat for a few years in the past) means once in a while you will have a rough crossing, almost always in winter. This type of up-and-down motion like the boat in the GIF, going into the waves, does not make me seasick at all no matter how big the waves. But you get side-to, rolling with the waves and it’s Barf City for me. Going side-to the waves also vastly increases your chances of capsizing so it’s a little terrifying. I don’t go on boats a whole lot except to go over to the mainland on the ferry and I avoid days when it’s really rough out.