With David Jason as the lead and also one of the producers, I expected a lot more than I got when watching this. The first half was pretty good and promised an intriguing finale, but the second part descended into a confused and unconvincing mess where the crew weren't the only ones to wonder what was going on. I got the feeling that some rather heavy-handed editing had occurred, both with the plot and the final production. There were glaring anomalies in the story line and the original theory of how the sub had reappeared after being missing for forty-odd years was completely ignored at the end (apart from a brief display of mysterious lightning).