Share this on Facebook
download .zip with all pictures
U-Boats could certainly fire underwater and often did. There are a few reasons they spent so much time on the surface. First, they had no way to recycle oxygen and so what they had in the boat when they went under was all they got. Second, because of relatively primitive battery technology they couldn’t stay under for long periods of time and still go places, additionally, because depth keeping was all manual, the boat had to be moving to maintain depth, so if you killed your batteries you are either gonna sink or float.
On top of that, they were significantly faster above water than below. 17.5kts was their max surface speed (at least in the case of the most common U-boat the Type VII), and their max underwater speed was 7kts. This was partly due to the hull design but when they were expected to spend most of their time on the surface it should be no surprise that they were higher performing in that regime.
It wasn’t until the Germans were forced to invent the snorkel that their submarines actually spent more time below the surface than above it. And that only came about because Allied ASW techniques were making spending long periods of time on the surface too dangerous for the subs.
Also, WW1 U-boats were all capable of firing while submerged as well.