To remove the OOF grass, you need to convincingly match the color and luminosity of the image behind the distracting elements. Because the grass is so out of focus, the scene behind it is visible - you just need to match the occluded scene with background it is part of.
I duplicated the background layer and used the clone tool on this new layer, with the layer blend mode set Color. Choose the adjacent background color and brush over the grass with a big soft brush to make the green of the grass turn bluish gray like the water (or dark warm black like the dog's fur).
Next, add a Channel Mixer adjustment layer and check the monochrome box. Set the blend mode of this adjustment layer to Luminosity - play with the sliders until the areas where the grass exist match in the background luminosity. You do not need a mask, you just need to emphasize green over red or blue. You want to keep the total percentage of the R+G+B at 100% - I think I settled on 10R, 40G and 50B. This should blend the grass area on the water with the water. Season to taste. You may have to do this step twice is the blend from some of the grass does not work on other grass. Now you can use this to clone in the luminosity and remove the bright soft stripe of luminosity that was left after you cloned out the color of the grass in the previous step.
do some clean up and then add back some contrast into the areas under the grass that had the contrast reduced due to the OOF grass. Paint that in and do your final tweaks.
kirk