How do I make a concentric coastline effect?

[Chashio]

@Sharpes: With the magic wand tool (with contiguous setting checked at top) select your water and invert the selection (from the menu bar under Select > Inverse or use the keypad: Ctrl+Shift+I). Then make a new layer and fill your selection with white or any color, then set the layer Fill % to 0% (in the layers panel underneath the opacity %). Do your strokes on that layer. There are actually a number of ways to stroke it. You might like this set of actions I created to speed up the process: Photoshop Actions: Fading parallel Coastal Lines for Oceans and Lakes If you need any additional help, just ask.

And here's a quick tutorial for creating a fading stroke effect using the OuterGlow layer effect: Fading parallel coastal lines with OuterGlow