You have to understand what sea sickness is, which is difficult because nobody really understands it. The inner ear is the organ that controls balance. On a boat, the fluid in the inner ear sloshes about, telling the brain that you are in motion. The eyes, which focus on the boat, tell you brain that you are stable with your environment. Your brain says "What the *****?" and orders your stomach to jettison your breakfast.
If you stay on deck and focus on the horizon, you may be able to sync the message that the inner ear and the eyes are sending. Some people can, some can't. Those that can't use drugs. Unless you have a lot more money and free time then most of us, you probably don't do enough boat trips to worry about adverse effects from long term use, so just experiment with different drugs until you find one that doesn't have unpleasent side effects.
By all means try the patch, for 90% of users it has no side effects, and it works great. While I don't normally get seasick, I used the patch once when I was doing a sailboat delivery from Hawaii to the mainland, which involves heading north for several days into big steep square waves. Crew mates who hadn't used the patch were chumming within hours, I was cooking bacon with no ill effects. About an hour after putting the patch on they were OK.