I have a couple of tips / suggestions. The first is that if it were me, id lose the bathymetry and make all the sea flat because normally you cant see under the sea. Now it might be that you need to know this in submarines etc in which case forget that but for above ground stuff I see no advantage to knowing water depth.

The other thing I discovered is that if you can get hold of a 3D model of something you like and you can get it into Blender then it has a nice feature called Unwrap into UV. What that does is flatten a model into 2D and you can export that image. Then what your supposed to do is draw on the 2D representation and texture it up a good 'un and then reimport that image and wrap it back onto the model once more. Now if after exporting the unwrapped image you texture it up then print it instead then you can form it back into a real 3D paper model by folding along the polygon lines.