100
Any of the ff:
submarines in WW2 could travel further than submarines of WW1 because of more efficient diesel and electric engines
WW2 submarines could be submerged for longer periods of time and could contain more crewman
submarines in WW2 could hold more weapons than WW1
snorkel invention allowed German WW2 submarines to charge their batteries and take in new air without to surface, could stay concealed
Give one way submarines have become better fighting machines in World War 2.