[quote=Slypheed]
That logic is valid for ships that use batteries to power their engines when submerged (ie U-Boat VII and variants without a Snorkel) where the batteries have less output than the diesels when surfaced. However, in modern times, where submarines are powered by engines that can run in both states (surfaced and submerged) they either loose a few knots, or even go faster submerged than surfaced. As well as being engineered to be hydrodynamic when submerged
[/quote]

We don't use diesels anymore, so US subs are 100% nuke. And yeah, they're designed to go fast underwater. You're correct.