What cracks me up about that pump KM, was that it was felt that it could not generate enough force to pump water when deep, and would fail at roughly 550-600 foot depth, so the max "safe" dive was set at 400 foot. The hull itself was most likely good to 700+ foot. The noise of the pump when deep was one consideration, but when you think about it, an electric pump motor's impeller, sitting in a sump of sea water, will deteriorate over a short period of time, and you can understand their reasoning... lol - I have had many a basement sump pump fail at the most inopportune time, such as when it is raining cats & dogs and water standing everywhere outside... "Honey - we need to get everything up off the basement floor NOW!" "But it's 2am!"
- now imagine that in the middle of a depthcharge attack, and you most likely are never going to be able to surface...
One other improvement on the Balao was the drive - quieter than the Gato, but I don't remember exactly why... I'm sure someone will pipe-in about that.
