I love the atmosphere - truly, being a ferry man with such a dramatic sky and bleak sea is inspiring!
I do think the game needs more "development". Beyond the handful of lines by each character, the game just plays the "same key" for 30 minutes, which gets very dull and kind of ruins the experience, to me.
Perhaps more thoughtful and dynamic music would help, as would writing (perhaps some poetry to keep in mind in relation to each character during the otherwise silent trips).
Also, just a nitpick - the crosshatching shader doesn't look great on the sky, probably because the colors are static, it ends up looking rather unnatural. Perhaps a noise filter would work better in this particular situation. It looks great on the remaining objects, though.
Either way, great job on this; the first couple of minutes alone are worth the remainder of the time!