Do they keep priests onboard?
If I become a sailor, how common is it for there to be a priest onboard who does masses and hears confessions?
Not having a priest is like not having a doctor. If something goes wrong with your soul, you're fucked.
Same thing with your body. Now, sometimes God miraculously cures your body or your soul if there is a problem with it, but we don't know when this happens and this is known only to him when he chooses to do so. Hoping for a miracle to cure your body is asinine if you could just take aboard a doctor and get the same effect, so I don't see why a priest is any different.