Check with your cruise line whether you are allowed to use one. I bought one a couple of years ago for a cruise we were going on (this particular ship didn't have laundry rooms) and ended up returning it as my documents said they were not allowed. I had thought it would be a safe alternative to an iron. But no. They are considered a fire hazard.
If your ship has a laundry room there will be an iron in there you can use. You can also hang your clothes in the bathroom and the wrinkles will fall out pretty easily.