>>> Concrete Ships

Well, there used to be quite a movement in home-building ferro-concrete craft. Apparently you can make a nice boat hull from this, if you do it right, but doing it wrong seems to be easy, and its hard to tell in a completed hull if it was "right" or not… until it falls apart.

Regardless, there is another side of concrete ship creation… the military/industrial world has built things from concrete for many years, including some attempts at ships… some successful, some not.

This is an interesting site covering some of that history.