Open ocean sailing bears little resemblance to coastal sailing. It can separate the "real" sailors from the dock queens, I assure you. I once took a very substantial boat on a delivery with the owner and his wife. First mistake. Oh, they ran around on the docks with their high dollar sailing clothes, rigging knife on their belts, and explaining to everyone that would stand still for a minute about how it was done. Lake sailors through and through. I literally didn't have the boat out of sight of land when the lady was sick as a dog. Done. Second mistake, and it was mine as well, was I needed to have the boat "there" at a particular time frame. (Note to self: never set a deadline for entering). I had every rag on the boat up, even sheeted down the courtesy flags trying to get that pig over on 'er chines because I was fighting 7 foot head seas, and a bad period. That boat slammed for two days. The owner finally fell out in the middle of the first night, and he joined his wife in THE FOREPEAK to ride it out. Wrong. Worse place on the boat to be sick. By this time I was sick, and with little recourse. Had to man the helm. Offshore, you can't just slide up in a harbor and get over it. The one time I went below at about 3 in the morning, just to take stock of the situation, I was holding on in the companionway with both hands, the boat was violently pitching and rolling, and the interior looked like it had been VANDALIZED. Everything you can imagine was in the floor. Because on the lakes they were accustomed didn't do that kind of thing. I laughed heartily, just like this: Ha Ha Ha. It truly was one of those times when I would have given every cent in my pocket to be off of that boat, all 4 dollars, and 36 cents. Was it miserable? HELL yeah. Would I do it again. In a skinny minute. And did with another boat almost like it a month later. Much more pleasant trip by the way.
Now, you can read enough on these sights to hear a thousand more experiences just like this or worse. But do not, do not let this stop you from doing it. Prepare. Be tough. Pray. Reach out man. It's one of the few of life's true adventures a man can still do. At least legally. In retrospect, I've loved every minute of it. And if it's all good, nothing's good.
And the only cure for seasickness is, sitting under an Oak tree for 12 hours.
But seriously, drink water even if you keep throwing it up. Then drink more.