My K/1 Combo class did this lesson. They painted the background first doing the sky white then adding blue, they then painted the ocean with blue, green, and white. We did not rinse between colors so that was one less clean up step. I had them wipe their brushes on scrap paper or their placemats.
While that was drying, I showed them our “magic square” trick. A square can be cut into 2 triangles or 2 rectangles.
They then made boats with the squares of painted paper. I often use my old demo lessons chopped up for things like this. I also have some art room helpers who will take the paint leftovers from a paint day and paint on “oops” papers.
That paper is made by my upper grade student helpers. While I am pretty conservative in pouring paint, there is always a bit of leftover paint on the supply plates and it is a good way to use that up. (Reduce, reuse recycle: it’s good for the budget)
They then cut and assembled the boats however they wanted to.