Factual error: Ian Fleming explains to March-Phillipps that the U-boats need "fuel and torpedoes, but they also need carbon dioxide filters, for oxygen." U-boats didn't have CO2 filters. They had the air on board when they dived, which, along with the batteries supplying the electric motors they used when underwater, limited the time they could remain submerged. There were several instances of U-boats being forced to surface after long periods of being depth charged; their air supply had been exhausted. (00:12:00)
Factual error: Throughout the movie, we see soldiers at the air base control center communicate with the aircrafts using an RT-524 radio transmitter. This radio operates in the VHF range, which is not suitable for communication with fast jets due to the Doppler effect. To communicate with jets, you need a UHF range radio.