I’ve realised I have a particular workflow for drawing coastlines in my maps. Here’s a quick walkthrough.
Each step is done on a new layer in photoshop, and I use a 5px hard round brush in each case with size set to pressure. However, all of these steps can be done in Gimp – or with a pen on paper (though you should use a pencil for the first step so that you can erase the sketch after step 1)
1. Draw an Outline
The key here is to get a rough shape of your landmass. This can be a continent, the coast alongside a city, or a tiny pirate island. Rough out the shape you’re looking for. It took me 4 goes to get to this shape and be happy with it.
2. Draw the hard coastline
Coasts are jagged and random. Let your pen wander, but use a fairly thick line – and try not to lift the pen off the paper. You can add beaches by allowing a smooth curve, and then go back to jagged coast.
3. Add an impression of detail
Inside the coast, add short sketchy lines. Some should follow the coast, others should move in from the coasts. Frame the beaches with sketchy lines coming inland – that helps them read better.
Now, with a thinner, lighter pen, draw smooth flowing waves around your coast. They should cluster tightly close to shore, and become sparser the further away. The waves should follow the shape of any wave closer to the shore.
More tutorials available in the tutorials section.