[Jimbuna]

The SH3 world is a "Mercator projection" - meaning that the round earth is being projected on a flat surface.
This results in a great deal of distortion in the distances between objects.
for example:
On the round earth it is a voyage of some 3,300 miles (give or take) from Brest France to New York harbor...in the "mercator world" of SH3, that distance is distorted to a whopping 5,300 miles...not quite TWICE the actual distance.
A type VII sub would have no problem travelling at an economic cruise speed from Brest to New York and back acting conservatively but in SH3 you would run out of fuel about half way into your return voyage.
Because the SH3 modders could not change the SH3 world from Flat.. to spherical, they had to adjust the in game range of the U-boat by increasing it nearly 3 fold.