The circle shaped parts in the red area. It looks like a sponge was used or something similar but I really don't know. I'm using acrylic paint but I can try watercolors if that helps.
Try dropping water on it while paint is wet. Rubbing alcohol should also work but paint still needs to be damp when either is applied.
I'm a real novice - BUT - I think I saw this achieved by dropping liquid (maybe alcohol) onto the canvas. This could get you started on some google search.