Using Photo Filter

Open our picture.

Then copy it using Ctrl + J. Call the new Layer photo.

Then go to Create new adjustment Layer and click on Photo filter.

We'll choose Cooling Filter (80) because we want to work on that lake and sky to bring its blue color. Choose value of 50% for density.

Now click on this icon (or press D letter on keyboard; this brings our default colors which are white and black). Press Ctrl + Backspace. This is because we want to mask adjustment Layer.

Now click brush tool (B on keyboard), select some brush, pick white as foreground color and start painting on black fill where the lake is and over the sky. You can zoom on picture with Z on keyboard.

Now we are finished with the blue color of lake and sky. Now we can use new adjustment Layer and make some changes on green surfaces but our goal was to change the blue color. More on using Hue Satturation adjustment Layer in next tutorial.

For a finish touch you can use Smart sharpen (Filter - Sharpen - Smart Sharpen) and sharpen this photo just a little bit.

Here is the final image

Enjoy.