He bowls overhand.
Meh, it's not quite like that. Subs transmit on the fathometer under most circumstances to avoid this very thing from happening. When going through the north pole - or anywhere where dodging ice is a concern - subs transmit active sonar to see what's in front of them.It has always blown me away that subs in EMCON (pretty much all the time?) basically fly blind through the water. Like the high speed canyon run in Hunt for Red October. I suppose they have pretty good INS positioning though. I remember seeing a documentary about Nautilus navigating to the North Pole the first time. They used an INS designed for high speed, short time (maybe the same one that went in the A6) and used it to navigate at very slow speeds for very long time. I know an INS can drift quite a bit in a short time.
Even with perfect positioning systems, it's only as good as the quality of charts, and doesn't account for unplanned obstacles
Obviously, I'm fairly ignorant about undersea navigation.
As an A-6 guy, I always likened it to flying a low level through the mountains at night, and turning off the radar, relying only on clock and chart and INS, no thanks