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These totally look like underwater reef shots. Well done, I especially like the colours in the last pic. I agree that changing your light source is probably the best way of introducing greater clarity to your images. The impression of being washed out might have to do with light bouncing into the lens. Can you elaborate? Is it all your pictures or only under certain conditions, with certain lenses, etc...? You might try using a lens hood if there's a glare problem or shooting with a circular polarizer if there's a problem with reflections. However, judging from these photos I don't really see a problem.
In post you can also increase the black point (basically a more finely scaled contrast).
Hope this helps,