During a recent trip aboard a cruise ship, I was stricken by a stomach virus that just wouldn't quit. Apparently walking around the ship for two days with this in me was ok, but once I sought help and got some medicine to stop things from coming out of me I needed to stay in my room for 24 hours. This was most troubling due to the fact that I couldn't leave the ship and go to the off-shore banking capital of the world, Grand Cayman Island. Did I mention this was my honeymoon? Let the romance begin.
To avoid getting stuck in your room be sure to pack some Immodium or Pepto Bismol and bring it on board. I don't remember if the ship security searches your bags or not but they don't sell this in the duty free. You need to go the infirmary to pick it up. When you go to the infirmary they throw you in lock down.