When looking for reference images, don't look for submarine. Underwater nature pictures, like whales and sharks, etc, taken by nature photographers are generally far better than photo's taken by military photographers.

http://poseidonwebdesigns.com/Dolphins/whaleindex1.htm

Two years ago I did a lot of work with the team that made the movie U-571, they were going to make a follow-up about a Gato class submarine in the Pacific (I had to model the submarine), so I did a lot of research on submarines, but as I wasn't going to render any of the shots I didn't do the research on the underwater rendering. Unfortunately their financing fell through and the movie never got made... missed my shot at the big time, lol.

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