You can clearly see the effects of NI in the 100% crops. The noise in the water behind the head of the bird is gone, and so is the noise on the gray feathers on its neck and in the lower left corner of the image. However, not unexpectedly the detail in the brown feathers on the left side of the image and in the upper right corner is gone. IMO this is not objectionable, because the removal of the noise in the feathers on the lower part of the neck makes for a much more appealing look due to softening of the harshness. The neck is a primary area of focus for the image, and you have done a good job of taking care of noise there in a pleasing way. Perhaps you are a bit lucky because the fish itself has no particular detail. If it did, the lack for sharpness from the de-noising could have been problematic.

Having said that, there is no reason to de-noise the whole image. You can either apply NI selectively to parts of the image selected with the lasso tool, or you can put the de-noised image in a separate layer, and then use a layer mask to expose the de-noised parts you want.