The following tutorial will show you how to create stunning 3D water scapes from scratch, using Photoshop or another similar paint program. We will not only be creating a realistic water texture, but will also be creating a convincing illusion of single point perspective.
Main Texture

After creating a new document, select a light shade of blue, saturated to 100%
for you foreground colour.

Select white for your background colour.

Either use a cloud filter to create a cloud texture over the entire image, or
fill with your foreground colour and paint in the clouds with white using a
large soft brush.

Select Image>Adjustments>curves.

Adjust the curves so the blue becomes darker.

The curves option allows you to maintain the hue and saturation of the image
while darkening the midtones.

You should see something like this:

Water Texture

Select the bottom two thirds of the image.

Copy to a new layer and darken -50 as below.

This is done to prepare the water image for the following filter which will
be applied.

Darkening the image will allow the highlights of the water to be better targeted
by the Plastic Wrap filter.

select Filter>Artistic>Plastic Wrap and apply the settings below

You should see something like this:

Water Perspective

Zoom out enough to be able to see at least 100% of the image size on either
side of the canvas.

Select Edit>Transform>Perspective and stretch the bottom anchors so that
the bottom selection is 300% longer than the image, or 100% longer on either
side.

You should now see something like this:

Water Form

Using the liquify command or the smudge tool, smear some bumps and valleys up
and down along the highlights of the water. Only apply the effect vertically,
using a smaller brush as you ascend along the image. This will give more definition
and form to the surface of the water. If applied properly, the highlights will
appear as if they are catching the light at the tops of these bumps, rather
than just being painted on a flat surface.

Now, restore the brightness of the image, but keep it a bit darker than the
sky.


Stretch the bottom image about 30 percent horizontally. This will relax your
new bumps and enhance the perspective of the water.

Sky Perspective

Select the portion of the sky that is visible above the water layer.

Adjust the perspective so that the top anchors are 50% longer on either side
of the image, or 100% longer than the original image.

You should now see something like this:

Finishing Touches

Using a soft brush, lighten a portion of the sky. This bright blotch should
not be completely white or completely round.

The object is to make it appear as if the light is breaking through and interacting
with the clouds.

Using a smaller, harder brush, whiten the center of the lightened area.

Do the same on the surface of the water. Be sure to measure the distance of
the lightened area of the sky, and create the water highlight the same distance
below the horizon.

Add some happy seagulls and your done!