It is a shame it is not far, far better because it is produced by Bavarian TV and almost the entire cast is German, but to get eight rolling episodes for world-wide streaming the writers have had to over dramatise and grossly exaggerate the 'plot' line or lines they have chosen to follow.
You have 'spoiled' a lot of the show already by your brief description, which is pretty good, and I am not going to add to that specifically but what made me switch off (after Ep 2 or 3) was the depiction of the U Boat crew (s). They are not likable in the slightest and in fact it seems the German producers have gone above and beyond to deliberately depict them as total scumbags at the worst, and annoying stupid couldn't-care-lesses at the least, and the officers are either weak, mutinous cowards or unbalanced murderers - no bull!
It is set in La Rochelle and good use is made of the old pens still in existence, but the sub plots involving Alsace Germans who struggle with divided loyalties (the heroine), undiscovered Jews, a thoughtful and sympathetic Gestapo officer contrasting with his collaborating and ruthless French police counterpart, 'terrorist' communist resistance fighters looking back in angst at the Spanish Civil War and the lost cause, American industrialists somehow involved in the R&D of the Type VIIc U Boats and really, on it goes with numerous other distractions to the battle of the Atlantic to the point of the viewer going "if this is the U Boat menace, what in the hell was Churchill worried about?"
What was really the final straw for me in the end that put this show to bed, was a gang rape scene involving returned-from-patrol sub crewmen and a local French girl who works in a bar (which is brutal and which I would say would never ever happen), and a stupid and cowardly mutiny (- ditto).
But hey, don't let me put you or anybody else off in the slightest, its on TV, sounds like its free, and its about WWII and subs so tune in and make of it what you will.
And I will add on a positive note that the production involving the hardware and CGI a/c and ships etc is very good.