I watched the first Das Boot which I thought was superb. I think it was a film which was later split down to show as a mini series. I watched the second Sky series and thought it was a poor imitation. More concerned with events on shore than the action at sea. The first did have some shore scenes but it was done to show the mind set of crews and what they had to face. I gave up on the SKY series after watching 3 or 4 episodes.