The first thing you should do with your seascape painting is to sketch an outline of the composition onto the paper or canvas. A seascape painting is usually more interesting if the horizon is not placed in the center of the scene. This means that either the sky or water will take up more space.
Let’s say that you are painting a cloudy day scene where the mood is windy and rough. You have already sketched the main subjects onto your canvas and placed the horizon line. Now use a soft large brush and brush a wash or thinned layer of blue with purple to darken it onto the sky area. While the paint is still wet add a touch of red to the top portion of the sky to darken it even more.
When the sky has dried, use white with a touch of the blue, purple and red added to it and start the clouds. When you paint the clouds remember that you want them to look large and stormy. To do this, paint them using large circular motions and leave spaces where the sky shows through. Your clouds should extend low to give the impression of depth. Take some of them beneath the drawn horizon line. To soften the top edges of the clouds, you can use a wadded paper towel, sponge or your brush.
Now you will add another layer of clouds. This layer will be either darker or lighter than the first. You just want to make them different so they look like a separate layer. Apply the second layer in the same manner as the first but make sure that you let parts of the sky and parts of the first layer show through. Your sky is now done.
Since you are painting a windy, storm scene don’t be too worried about keeping the horizon water line too straight. Just take your water color and using horizontal strokes, paint in the sea. A good color to use is ultramarine blue with hookers green. You should stay away from using straight blue. In this example we will paint the water in all the way to the bottom of the canvas. As you work your way forward or downward loosen and let the waves show with your strokes. The water will be lighter in the rear and darken as you come forward. Add some green and purple and even brown to darken the water as you come forward.
To accent the swells and water movement, use the brush edge and add lighter color along some of the waves. As you move forward, the waves will become larger and more visible. Add a few dabs of white to indicate splashes. If you want a particular wave to really sparkle and stand out add some yellow to the top part of the wave. The yellow will make it look transparent.