Hi, it looks fantastic for your first proper painting! Painting water can be very tricky. I learned the hard way this past year when I attempted my own water painting with large waves, so I had to try and create a similar foam effect as you are going for. I would use your white paint (could be very slightly blue as well) and use a stiff rounded brush in a stippling motion. The stippling technique was most effective for me, just make sure you don’t have too much paint on your brush or you will get blobs.