In addition to running my art camp last summer, I also stepped in one day a week to teach art with a general kids camp. This camp had weekly themes, such as the circus and the great outdoors. For the underwater themed week I decided to have the kids create these painted jellyfish. We used tempera paint in the primary colours to create up to 3 jellyfish. I had the kids first paint a frown line for the umbrella top of the jellyfish, then 3 small smiles for the bottom to create the jellyfish's shape.
After painting the entire body, I demonstrated how to add a dot of paint and then water to create the tentacles, holding their paper up vertically and slowly moving it back and forth to create the wavy lines. The kids loved this, there were lots of oohhs and ahhhs as if I was performing a magic trick. To finish off their jellyfish paintings the kids added splatter bubbles. The end results turned out fantastic, and more importantly the kids really enjoyed the process.
Like this artist who wanted to create a red, yellowish, and orange jellyfish instead, you could have students use primary colours to create 2 of their jellyfish, and then mix them to create a third secondary colour for their last jellyfish.