To appear more realistic, pull back Smart Tone to about 22. This gives a hint of detail to the trees in the right, similar to what a reflection on the water might cause. It also brightens that patch of sand to the right.
Enhance Saturation, Vibrance, and Color Contrast
At this point, let’s turn our attention to the colors. Play with the Temperature slider in the HDR Basics panel to add some warmth to images like this sunset. Then scroll down to the Color panel and tweak the Saturation and the Vibrance sliders.
Depending on your image, you may need to bump these either up or down. Just avoid taking them to their extremes; generally, somewhere between 5-20 will be a good range. You can also bump up the Color Contrast slider, which controls the contrast between primary and secondary colors.