[Yossarian]

I'm ignorant on submarine construction: do the cross-sections of other subs look like this?

That looks like what - 10 inch thick or so steel sandwich walls on the sub?

I assume the other outer 10 inches of exterior is the ballast / dive tanks?

Can a FReeper Submariner mention what they think of what they see in these pictures?

[burzum]

It's not 10 inches thick. Otherwise it would never have a chance of floating. What you are seeing is basically a large cylinder with a flange on the end (which makes it look thicker than it is). Around the cylinder is the ballast tanks. The steel is probably 1-3 inches thick (depending on how deep they wanted to go).