Being on a ship means that you are around loud noises, rumblings, and things that will make an automatic battery turn itself on. The contacts in an auto battery are fragile ones attached to a diaphragm that respond to the vacuum of a breath to actuate. Anything that causes sound pressure waves at some amplitude can actuate those contacts, maybe in your pocket, and kill the battery or the atomizer over time. I've read stories about people at rock concerts suddenly feeling a hot sensation in their pocket and having to remove the auto battery when not vaping and putting it back in to vape.
Manual batteries have a 5 click on-off function that is like a safety. You definitely want that if you carry it in your pocket. I don't know if the auto batts have that function.