Someone somewhere needed a large number of cargo vessels built quickly (think WWII liberty ships, but those weren't made of wood), so they brought in a bunch of cabinet makers to bolster their shipwrights. It worked great, until the ships built by normal woodworkers saw significant wave action, at which time they broke up and sank. The punchline being that, on land, rigidity is the primary constraint; if you build it not to be floppy, it will be plenty strong. At sea (and especially in aerospace), strength is primary; if you build it to be rigid, it will be too heavy and if you build it to be not-heavy, it will probably fall apart.

An amateur can build a fairly large boat (although usually to plans by an actual naval architect), and a small boat can make it across an ocean, but if you're serious about schlepping things around, the design constraints for ships aren't much looser than those in aerospace.

[1] Maybe this, although that's not the cover I remember: http://www.amazon.com/Structures-Things-Dont-Fall-Down/dp/03...