Now take color #335400 and block in some seaweed clumps with the paintbrush.
Make a new layer above the “ocean floor” layer and title it “coral 3”.
Now use the same color to add more clumps of sea weed.
Switching back and forth between the “coral 2” and “coral 3” layers, block in the shadows with color #223700.
Highlight the grass with color #457200.
Now, going back to the “ocean floor” layer, use the burn tool (400 pixels wide, soft edged brush, 49% exposure, midtones mode) add shadows to the ocean floor. These shadows are accentuations of the previous shadows, as well as those cast by the sea weed and corals.
Set the dodge tool to 30 % exposure in highlight mode (600 pixels brush) and highlight the ocean floor.
Make a new layer above the background (title doesn’t matter).
Now, using a 23 % opaque brush and color #BE7709, make the ocean floor appear to disappear into the distance. This will require some layering, with the least amount of layers in the distance, and them building (becoming more opaque) as they approach the bottom of the screen.
Now, using the dodge tool set to 30%, layer and swirl across the background to create an illuminated water effect.
Now, going back to the coral layers, swipe the dodge tool back and forth across the sea weed and coral, to make it look like there is spattered light falling on them.
Lastly, make a large shaft of light filtering down on the background layer, and then use the dodge tool to make it appear to be falling on the “ocean floor” layer, as well as the other coral layers.
And you are done! The second half of this tutorial describes how to create different sea creatures and finish the digital painting.