Hi Robert,

Good point... However, 418 feet is 127 Meters, but 280 Meters is about 918.6 feet. You will more than double the Atm pressure at that depth (12.7 Atm Vs. 28 Atm).

I believe both the Main pump and Auxilary pump in the U-boats had a maximum effective depth for pumping was 110 meters. Therefore, at 280 meters, the U-boat is not going to pump any bilge warter into the sea....

Regards,
Don_