Try out the ancient Japanese art of Suminagashi, or "floating ink."
Create intricate patterns by transferring floating ink from the surface of water to a sheet of paper. Begin by filling a small tub with water, and gently drop black ink from a brush onto the surface of the water. Immediately follow the ink drop with a drop of soap and continue to alternate between the two. Before you know it you'll have a rippling pattern of organic rings.
Once you've filled your surface of water with ink designs, quickly dip a sheet of paper onto the surface to absorb the ink. Remove the sheet of paper and admire your design. Let it dry.
For a thorough exploration of Suminagashi, check out Hazirah Kadir's Skillshare class, Beyond Beautiful 2.0: Suminagashi Technique