I watched the final 4 episodes of Das Boot. One critic observed that a few years ago you would call it unmissable but such is the improvement in European productions that he down graded this to hugely enjoyable.
I would not have gone as far at that.
There were 2 parallel stories, one on the U-boat which owed much to the original film and the other the Resistance and occupation of La Rochelle.
The latter story had a feminist makeover as, rather improbably, the leader of the Resistance cell is an American woman who fought in the International Brigade who seduces Simone Strasser (Vicky Krieps) who works as translator for the occupying Nazis. She provides a link to the U-boat as her brother is the radio operator.
As to the U-boat section of the narrative, it was never that clear what was happening to the vessel. Two of the best scenes in original film were omitted: the banquet given to the U-boat crew who, after all the time at sea, gorge themselves with no manners and the final bombing of Bremen where the U-boat was berthed.
The formal almost courtly way he pursues Simone is contrasted with the ruthlessness in which he puts the resistance down assisted by the Vichy Milice head of police.
This attention to political and local detail made the romance between the two women all the more unlikely and inserted for the modern audience. Add to this that the stories have to be extended over 8 episodes of one hour each.