If you, like me, watch this hoping to see a Japanese "Das Boot" one of three things will happen:
1. You fail to realise that this is not a Japanese "Das Boot". You won't like the film and you will leave a 1-star rating.
2. You do realise that this is not a Japanese "Das Boot", but don't like what it in fact is. Ratings will range from "I didn't like this, and that's all that counts" 1-star ratings to good ratings of "while I didn't like this, I can appreciate the movie for {how it was made/story line/whatever}".
3. You do realise that this is not a war movie but in fact a science fiction drama in a world war II submarine setting, and that is something that you at least don't immediately dislike just because of that.
Once I came to terms with this being a science fiction-movie I actually started to enjoy it. I like the fictional story line as well as the science fiction parts of the movie and the movie feels very good made. If I watch it again starting with the right expectations it's even possible that the rating will go up another star.
I think that where the movie falls short when compared to other movies en large is just the mix of genre and setting. It's like the Caprica TV-series, said to be a Sci-Fi Dallas. While not a bad series in itself people who like Dallas doesn't necessarily like Sci-Fi and vice versa, and therefore the series gets a bad average rating. I can therefore understand the low average grade this movie gets despite that this movie actually is quite good.