Fankly I don't care for the ship idea at all. Hunting down that interesting blacksmith, however, has flavor and could serve as a way to buff your PCs that are havng problems instead of bringing them down a notch. Perhaps he is reclusive and lives on an island in the center of the bay, what is in the water? Does he only come out at night? What if his ritual is sinister and includes more than just salt water?
Minimal old school sub, not bad. To improve I would add some details to differentiate the sub from the movie. Some ideas might be giving the villagers something other than a stash of weapons to protect, or a different motive for the bandits to be stealing their grain.