Create new layer. Name it whatever you want and select Elliptical Marquee Tool. Then make selection of a circle area near the top center of document. Size close to 100x100 px.

Note: To draw a perfect circle, press shift while selecting.

Hit "x" key to change foreground to background color and set foreground color to #F0FAFF. Then fill selection on the current new layer with this color. To draw the lunar surface, select Filter > Artistic > Sponge and adjust the following settings to this:

Note: You can set your own values if you chose another document and moon circle size. Moreover you should try to set your own values because with this filter you may get different results with the same values. Just try to reapply this filter until you get the proper result. After applying this filter you can Undo [Ctrl+Z] this action and then press [Ctrl+F] to select last used filter once again.

In my case, I kept looking at the moon in the sky through my window to compare results with the real lunar face... But after a few vain attempts I settled on this look:

I think our moon has a gloomy little face. Let's fix it. Select Image > Adjustments > Brightness/Contrast and set it to the next:

To make our moon look more realistic, add some blur by selecting Filter > Blur > Blur More. After that, put a daub of radiance around it. Right click on the moon layer and select Blending Options. In the Layer Style window set the Outer Glow settings to this:

You may set your own glow size value.

And now you've got your own moon.

Draw the Sea.

I decided to use Fibers filter for the sea. First, you need a new layer. Fill it with dark color (your background color) and select Filter > Render > Fibers. With the Randomize button you can try to get something like this:

Next select Edit > Free Transform. You need to rotate fibers. Right click on it and chose Rotate 90° CW. Then transform and move these fibers till your picture looks like this one:

Miniaturize it vertically and stretch it horizontally. Move to the bottom of the document and hit enter to commit.

Notes: To view full size of layer content, press [Ctrl+0]. To stretch from the center, press and hold Alt key while dragging.

Select Filter > Blur > Gaussian Blur to add some blur to the layer. Radius must be about 1.0 px.

Change the blending mode of the sea layer to Overlay and press the Add Vector Mask button:

Select the Gradient Tool and fill the layer from the center of "water" to the top as shown below:

Fine! Now you have the moon and the sea, but where are the stars?

Draw the Stars.

The easiest way to draw stars is to use the Reticulation filter from the Sketch group. Create a new layer. Chose the Rectangular Marquee Tool and select the area where you want place your stars (about 1/4 document size on the top). Set foreground color to white and fill the selection. Now you may deselect [Ctrl+D]. Note that background color must stay our dark sky color. Select Filter > Sketch >Reticulation and use these settings:

After pressing the Add Vector Mask button, choose the Gradient Tool and fill from the top to the bottom of current stars layer the same as we did with sea layer but in the opposite direction. Drag the layer to change its order next to the background layer under all other our layers and here are the stars!

But I prefer a another, a bit harder way. Choose Brush Tool. Set size 5 px for the brush

and randomly draw some stars in the sky like this:

For more realism you may try to draw something similar to the constellation of the Great Bear!

Then set brush size to 2px and confusedly draw some more stars of a smaller size. As you know, such bright stars are a rarity so change the master opacity of the stars layer to 50%. To draw distant stars, duplicate this layer and change the master opacity of the new layer to 30%.

Select Edit > Transform > Flip Horizontal and move it a little to the bottom. Hold and press [Ctrl+Shift] and move down. You can move this duplicated layer in this way as you want to prevent the superposition of stars. Just try to get a more or less realistic picture of the stars.

Draw the Light.

Create a new layer once more. Select the Brush Tool and set its size to 9px. Hold shift key and draw a vertical line from the bottom of the moon to the center of your sea. Now press [Ctrl+T] and stretch it out like this:

To make it, press and hold [Ctrl+Shift+Alt] and drag the lower right corner to the right. After this, select Filter > Blur >Gaussin Blur with something about 100px radius or less. As a result, you've got the soft radiance of the moon.

Draw the Reflection.

This is the hardest part of the tutorial. To draw the moon's reflection on the water you may use the Wind filter as a basis.

Create the final new layer. Select the Brush Tool and draw a small vertical line with the previous settings (9px) like this:

Then select Filter > Stylize > Wind (method Blast and direction From the Left). Repeat this step but with From the Right direction.

Press [Ctrl+T] and transform this formless object into this:

Apply Filter > Blur > Motion Blur with settings shown below:

And make it smoother by selecting Filter > Blur >Gaussian Blur:

It seems a bit ugly. But change the layer order and master opacity and you will see quite a good result. Place this layer under the "Sea" layer and change master opacity to 35%: