We went for a big ship cruise experience aboard NCL Epic r/t Miami.
I carried my fitbit with me and counted my steps. I like to set out at 6am and walk all of the cabin decks. On Epic that was 7 decks which took me an hour. As you can see, that was ~5,800 steps and ~2.7 miles. Add in the rest of the days steps and I had no trouble hitting my 10,000.