I enjoy historical war dramas - which from the outset this 'appears' to be. I have no problems with things taking liberties historically to move a story along, but this movie takes on all sorts of Hollywood tropes that even Hollywood has shied away from over the years... at points I felt like I was watching a comedy try to be a serious movie.
For one, the sole basis for the plot of Belgian resistance fighters delivering uranium to the US isn't a feasible plot. The US mined their own uranium and also had an ally in Canada to provide it as well. There was no need for Belgium to supply this for any reason.
Why they have to venture to Africa to pick up a stolen U-boat to make the delivery isn't made clear. This would be feasible if they had to visit a uranium producing country first, but they don't. Instead they go through a crash course for a few days of how to operate a U-boat at the hands of a former U-boat captain.
When they finally get into the submarine, mysteriously one of the characters knows how to detect for torpedoes, enemy ships and enemy submarines. It takes years of training for submariners to even become qualified to sail, let alone operate their individual stations.
When a torpedo slips out of its winch and falls on a crew's legs, thereby crushing his legs below the knees, he mysteriously stays conscious the entire time. Furthermore, he doesn't almost immediately bleed to death - which seems infeasible when you consider your femoral artery runs down your legs and would have you bleed to death within minutes if severed.
They only tournaquet his legs when they go to amputate them. Of course, this is also laughable because the whole time a fellow crewman is plying the amputee to be with alcohol - which thins the blood and could also have him bleed to death. They don't even use the whisky to disinfect the wound! This whole series of scenes is laughable.
When the Germans come aboard to visit, they don't salute. Instead of being treated and helped aboard the sub on deck, they somehow managed to board the vessel in the midst of heavy swells... Not to mention they just let themselves in and climb on down.
Despite none of the crew being in regulation German Navy uniforms - which would be the order given when visitors boarded their sub, no questions are asked of the faux submariners. When it all goes south and the faux submariners are detected, people are shooting at each other in a submarine with an abandon - also an unlikely event for the time because the bullets could pierce the hull!
Once the German officers are killed, a Belgian resistance fighter uses a sniper rifle to shoot through a German enemy ship's main gun bore and it all somehow just magically goes ka-boom! The sniper does this in the midst of severe ocean swells, during a heavy rain storm and visible droplets of water on her scope. It's just far too convenient and lazy writing.
When this happens, the German ship rams the u-boat and runs over them as they dive, instead of using one of her functional guns or depth charges to destroy the sub. It's explicitly stated in the dialogue that this was a German destroyer class ship, so it would have had jmore than just the one gun and definitely been equipped for anti-submarine warfare in the middle of the Atlantic Ocean. But hey, that doesn't make for good cinema, now does it?!
That all said, the German destroyer manages to sink the U-boat. This is perhaps the most realistic and well shot portion of the movie, until of course one of the submariners decides to get into a torpedo tube and be shot out into 150+ metres of the bottom of the Atlantic Ocean to save his daughter drowning from another compartment in the sub. Not only does he manage to do this without any air supply, he doesn't end up being crushed to death fronme the pressure end up with hypothermia, manage to drown, or even end up with the bends when he comes back (with his daughter of course) to a pressurized compartment.
There's just far too many liberties taken in this move to make it believable. It tries to present itself as a historical drama, but it goes through far too many movie conveniences to make it enjoyable. If you don't mind completely turning your eyes away from glaring plot holes, historical and physically impossible feats, then by all means dig in. Das Boot this is not. A definite opportunity missed.