Draw a light horizontal guideline for the waterline
Sketch a series of curved, repeating lines for the wave tops
Add larger arcs behind the front wave to show depth
Connect the curves with flowing downward shapes
Vary the height and spacing of the waves for a natural look
Add smaller ripples between the larger waves
Draw the foam using short, jagged, irregular lines
Thicken the underside of the wave for volume
Shade the lower parts of the waves more darkly
Leave the crests lighter to suggest reflected light
Add motion lines or curved streaks to show movement
Erase rough guide marks and refine the wave edges