Goofs

The Submarine Escape Immersion Equipment is ineffective at 1150 feet (350m) due to the great amount of pressure. The suit is only effective down to 600 feet (183m).

The divers at 90 meters must breath helium-oxygen mixture instead of normal air, or at least a mixture made of helium-nitrogen-oxygen. This would significantly alter their voice. Normal air at 90 meters leads to oxygen toxicity and furthermore it is impossible to calculate their decompression that should be anyway longer than 200 minutes.

When members of the crew enter the U-boat, they see the remains of a Nazi sailor chained to a pipe. Peters (David Threlfall) suggests that the U-boat crew must have been driven to cannibalism. However, the submerged U-boat could not have sustained life for a prolonged period of time; having a limited oxygen capacity (approx. 24 hours). The crew would have all died long before having to resort to cannibalism.

Once the divers enter the U-Boat they are no longer attached to their umbilical cables.

Foxtrot class submarine had 3 shafts with 3 main electric motors (and 3 diesels). Breaking one shaft would not stop the sub. It would have made more sense to spill a few battery cells and they need cables from the u-boat to jump the dead cells. That would have been accurate, as batteries were volatile.

They said ballast tanks were ruptured. (does not really make any sense, as these tanks are already fixed wide open at the bottom) If so, sub could have not been raised with propulsion only. If ballasts were in fact OK, then no need for the engines to surface, just blow the ballast by compressed air. One man is enough to open the blow valves for the main ballasts.

One and half of Cable Length is equal 277 meters, not 208 as Blackie said.

Robinson argues that Turkey has a naval base only "20 miles up the coast from Samsun." Actually, it's 178 miles to the east.

A mechanical failure forces them to go diving to the wrecked German sub for a replacement part. Subs like this have two complete diesel-motor-generator sets, and two complete electric-motor-propeller sets. No single component failure would immobilize both. Separately, the failed/replacement part is described as the "crankshaft" and indeed the film shows them bringing one underwater, fitting it, and then a crankshaft spinning away. But a crankshaft is an internal part of an engine, connected to pistons via con-rods, and that's exactly what they show. But it's not connected to anything of the sort. This makes no sense, but is I guess a cheap technical effect. Perhaps they wanted to represent a thrust bearing; those rub and wear and spark if they get dry. Even so, there's one each side, for each propeller and its shaft; no single point of failure.

The notion that a privately owned sub could depart Sevastopol without Russian and possibly other forces tracking it makes the whole concept of the film implausible.