Depending on the effect you want, sea foam may be created in thread or melted felt. The scale of the images makes a difference. In The Shore piece below, the foam is close up and larger. It was the perfect place to use some melted felt. In Dolphin Play, the foam is distant, so small #TwoStitchMagic zig zags were the perfect size.
Usually when I melt felt, I secure it in a wooden hoop or open frame so that it won't curl up when heated.
But for the foam rolling on the shore, I let it curl, as foam does. You can see the thick, curled edge in the lower left. This added a third dimension to the piece, as did the gathered and wrinkled top fabrics which were overlapped, squished together, and sewn in place. Another unusual part of the piece is that I dyed batting (the light blue areas), and let it show through the top layers.
Directions for #Two Stitch Magic stitching is available in video form from the store on this website.
More information about melting felt is on this website too, under 'Art.'
Give it a try!
Please shoot me a message if you have questions.