Step 10

Add a layer mask to the light source layer and use the Gradient Tool in the layer mask to hide the area that is shown over the water – basically we want to show the light source only on the sky.

Step 11

Let’s create some thin waves that will separate the surface of the water from the underwater. First we will make a custom brush that will use for waves and splashes. Select the chalk brush and open the Brush window (Window > Brush). Use the settings shown below to create a dynamic splash brush.
Save the new brush preset (otherwise when you’ll select another brush these settings will be set to default) by clicking on the button shown below in the Brush window and choosing “New Brush Preset”. Give it a name (I named it Dynamic Splash) and click ok.

Step 12

Make a new layer and use the Dynamic Splash brush you created at the previous step to create some small waves/splashes on the line that separates the surface of the water from the underwater.

Step 13

Create a new layer and change the blending mode to Overlay. Use the standard chalk brush (color – white, size – 2px, opacity – 60%) to create some more random squiggly lines over the splashes we created at the previous step.

Step 14

Create a new layer and set the blending mode to Color Dodge. Use the same chalk brush you used at the previous step to create some more shiny lines that will separate the water surface from the underwater.

Step 15

Let’s add some marine creatures to our scene. Open the file “Shark”. You’ll see multiple versions of the shark – select one you like, copy it and paste it in our scene (use the Rectangular Marquee Tool – M – to make a selection of the shark you like). Convert it to a smart object and place the shark as shown below. Lower the opacity to 30% to have the shark blend with the water.

Step 16

Create a Levels Adjustment Layer and use the settings show below to darken. Clip this layer to the shark layer.

Step 17

Make a new layer and set the blending mode to Overlay. Clip this layer to the shark layer and paint some subtle highlights (with a round soft brush and white as foreground color) as shown below.