I thought about this... and it sounds fun, but in the long run I think i'd rather spend more time hunting than navigating. This game can sap 5 hours of my life in a hurry as is.
It's realistic in that there was no GPS like we basically have now... It's unrealistic in that on occasion a Kaleun may double check the work of his navigator, but irl, he probably left most of it up to him.
There's a reason why there is more than one person on a u-boat.