I've built a few Fiddler's Green paper airplanes, as has a friend of mine, so I know it can work work in this material. If the folds, cuts and bends are done carefully, you can construct very detailed 3D models.
I've seen plans for a few paper ships, but nothing ever as detailed as this.
http://www.papermodels.pl/index.php?topic=6736.0Too bad I can't speak Polish to congratulate this guy and invite him to join our website. He's done an excellent job making a paper U-boat. Looks almost as detailed as the ones we have here, with all the flood holes, CT insturments, deck gun parts, railings, etc.
As far as I can tell by looking at the sequence of photos, it's all built on a keel and bulkhead plan, with the pressure hull and casing as separate parts added on in sections to get the proper shape. The bulkheads and keel were glued to card stock to give some stiffness, and then spacers or stringers were added between the bulkheads for more stiffness and to give a larger surface area for gluing. Then the boat was 'skinned' with the various plates held in place by wrapping thread around it until the glue dried.
It looks like every hatch and cover, and many of the hull and casing plates, were all separate pieces to add realism.
VERY impressive!!