ok gents, i just watched it.
it's...ok. if you have no idea about submarine warfare and tactics i gues it's a competent WW2 action flick. everyone else will facepalm pretty hard, pretty often. it also has impressive visuals.
to summarize the movie in one sentence:
if you ever wanted to watch a type vii boat engage in a surface gun duel with a fletcher class DD
and a flower class at the same time at literal point blank range - this movie is for you.
-SPOILERS BELOW THIS POINT-
and many more that i already forgot. anyway. you can get a quick uboat fix in, but nothing more. i enjoyed it...a bit