[Crosseye76]

And don't forget guys, your not just talking about the pressure hull here.

A Submarine is a ship, not a an unbroken tube of steel. A lot of these dive limits were not based only on the yield strength of the pressure hull.

They were also based on all the many other systems that had to stand up to sea pressure. Shaft seals, Periscope and other mast glands, depth sensing inputs, Etc.

I can't dig up the source now, but I seem to remember a comment about the U.S. pumps. Based on a WW 1 design, they could only overcome sea pressure down to a certain depth, so they could not pump overboard below 300 - 400 feet or so.

Every time we went below a certain depth on the 643 boat, there was a "Deep Submergence" bill. This closed some un-needed sea pressure exposed systems (The Depth input line to the Hovering system for instance) and gave instructions on systems to monitor and keep an eye on.

We never worried about the Pressure hull giving up the ghost, it was FAR more likely that a problem would arise from all the various holes in that hull than from the hull itself.