I don't take cruises. A recently learned that crimes on cruises are prosecuted in the country in which the ship is registered. That alone is enough for me to avoid stepping on board.

If I were to take a cruise (I don't), then I would make sure the ship is registered in the United States. I would bring the standard personal survival kit (flashlight, fire starters, whistle, first aid, mirror, etc.). I would also bring extra snacks, extra batteries, bandanas, water purification, toilet paper, plastic bags, and a personal life vest.