Dark Water by Aaron, Impact Forums
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Open a new document about 500x500
Press 'd' on your keyboard to reset the colours.
New layer.
Goto - Filter > Render > Clouds
Filter > Render > Difference Clouds
Filter > Sketch > Glowing Edges
Settings :
Edge Width : 2
Edge Brightness : 12
Smoothness : 5

Now,
Duplicate the layer.
Goto
Filter > Distort > Wave
Set the Blending Mode to Lighten.
Leave everything default.
Here is the final result.

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That's the end of this very basic tutorial. Hoped you liked it.