Never on a ship but I lived with a ghost in my last house for over 20 years. He was extraordinarily active when we moved in, for about 6 months, and then again when we moved out. My mother-in-law suggested an exorcism, I kid you not. The ghost was that strong. You could hear footsteps on the stairs all the time and so forth. I had a babysitter who would never come back after one evening!