One noticeable effect of the four-decade gap since the film is the improvement in special effects, even on a TV budget — the scenes on the water, especially during battle, look immeasurably more lifelike. They’re also not as beholden to standard submarine-story jargon and images — less dashing up and down the passages, fewer references to “silent running” — though those repetitions were kind of the point of the film, and aficionados can be excused for wondering why a new “Das Boot” was necessary. (Fans of Petersen’s opus will also miss his eye for composition and lighting — the way he made tableaus of sailors watching dials and listening for ships look like supplicants in an old-master painting.)

The real, and perfectly natural, change is that the story has been expanded into a conventional modern TV production, with its international cast and its multiple intertwined plots to fill the many hours. (Episodes run 55 to 60 minutes, commercial-free.) There’s more to see, but it’s more diffuse, and the continual cutting between the land story and the sea story gins up the suspense while making individual scenes more perfunctory.

For three-plus episodes, those stories build in a reasonably interesting and plausible fashion, proficiently staged by Andreas Prochaska, director of the entire season. Hoffmann, the captain, deals with rising tensions on U-612 — he’s unfairly seen as a dilettante and a coward — while Strasser is gradually radicalized through her contact with a resistance leader who happens to be American (Lizzy Caplan). That character, with her wounds from the Spanish Civil War, is pretty familiar, as are the shrugging French cop (Thierry Fremont) and the courteous Gestapo agent (Tom Wlaschiha). But they inhabit a well-made and entertaining, if prosaic, period war story.

Then, about halfway through the season, both the land and sea tales take radical, sensationalistic twists. The one involving Strasser is romantic and not in any way implausible, but it pushes things in a melodramatic direction. The one involving Hoffmann is dire and seems highly — let’s say profoundly — unlikely for a German crew at the height of the war, two years before D-Day. (It’s also a strange dramatic choice in that it removes a central character from a long stretch of the season.) But the OMG factor is high, if that’s what you like.