I fully understand your concerns Phil, and the original is a classic's classic, but no matter all of the dramatic side bars thrown in, it can be rewarding TV.
I refer you to the five season run of "The Last Ship", seen here in the States. Most of the plot was contrived, but at least partially made up for by seeing the couple of Burke's that portrayed the fictional Nathan James at sea doing their stuff.
Might be a little harder with a U Boat, but as far as I know two still exist for on board shots, one in Chicago a Type IX, and another in Germany, Type unknown.
Please keep us abreast as you watch and the series progresses.
The new 8 part TV series of Das Boot starts on British TV next Wednesday (6th February) on Sky Atlantic, with the showing of the first two episodes.
Each episode is about 1 hour 10 mins long, with whatever amount of Ads Sky Atlantic choose to show.
The series is described IN THE LISTING MAGAZINE as both a "sequel" and a "re- Boot " (which I assume is a feeble pun). It is set in the Autumn of 1942.
UNFORTUNATELY, a feature on the series explains just how dire the series is likely to be ;
"... the eight hour series also widens the class of characters ... There are Gestapo officers, French Resistance fighters, British SOE agents and rogue Americans." ! ! !
The (?) rogue American has been arrested in Germany and the U-Boat is sailing to a mid-Atlantic prisoner exchange (even more exclamation marks !)
Also (!) the senior Gestapo officer is in love with a woman French interpreter - who (just to justify some more exclamation marks !) is in a relationship with a female American guerrilla (or would gorilla be more realistic ?)
I think that the preview seems to describe a comedy.