Big Surf in Watercolor

I usually paint ocean waves in oil because foam is difficult to show in watercolor.  I am purposely having lots of foam in this 8x18" painting so that I can learn from the experience.  This will require saving the white foam with masking fluid and I am making sure that I use Arches paper which is tough and will allow the mask to be rubbed off easily when dry without peeling the paper. The rough sketch which will be transferred to my 300# Arches cold press paper.  One of the reasons for the long size is because of the shape of the wave and my wanting it to fit nicely in a 10x20" frame with one inch mat around it.  If all fails, I will paint it in oil!