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The processing looks fine. I'm always blown away by the color of that lake.
Lake levels? The only planar features that I see are the tilted limestone ledges, with are also causing some linear features through the forest.
I'm sure the shot was level, but there is an illusion that the lake level is higher towards the outlet on the right. In such circumstances, some people prefer to ignore the bubble level and rotate the image to at least decrease the illusion. However, if it doesn't bother you, don't change it.