Jack, I've wondered how on earth concertinas EVER became associated with sailors! The very last instrument I'd ever take into a salty damp environment would be made of soft-wood and leather and hardened cardboard, and get its sound from tempered steel reeds, and suck the salty damp air into its dozens of, tiny, hard to access reeds. And they were a new instrument and very expensive then.
Hollywood, I suppose.

Interesting reading there.