Re: Marinas while in transit
Call ahead. They do have phones, right?
And most will have a mail slot in their door, or some other provision. In some out of the way locations I've seen a note on the door telling out-of-hours visitors what to leave, or what they can take. (i.e. taking on water during closed hours.)
But tying up without permission is simply trespassing. Worse than bad form, it usually is actionable. I'd be very reluctant to do that when phones and radios are so common these days.