It was a physic connection between Stranger and his boat. I don't remember them mentioning actual conversation via sound waves between the two - maybe they did
Anyway, one thing I've noticed in the picture PA posted, is that it looks nothing like Oddworld. I could have sworn it looks like Zelda: The Wind Waker. As the colours are bright, and match suitably. The boat, looks like the Red Lion and that building in the background looks like a would-be Hyrule Castle.
Alcar...