So, Lezales asked me how I got the coast effects in my current WIP thread, A Political Map Korachan and its environs following the Events of the Great War...WIP (yes, long name, it’s a period thing!) so I thought I’d work up a quick wip for this.

1) Use a white base map. On a new layer on top draw the coastline in a hard black pencil tool. The land part was filled in with black to create a good contrast
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2) Select the land and create a new layer (called land) and fill the selection white. Add an outer glow layer style, with the following settings, using a nice blue colour. Add a stroke layer style with the following settings using the same blue.
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3) add a new layer and fill it with a striped pattern and add a layer mask, hiding the land area.
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4) You’re done!

obviously you can tinker with the outer glow settings to get somthing more to your liking, as well as rasterising the wave lines and blurring and/or distorting them