Back in our school days, well before personal phones and all that, we'd often make folded paper water bombs, eg: https://www.google.com/search?q=origami+water+

Back in our school days, well before personal phones and all that, we'd often make folded paper water bombs, eg: https://www.google.com/search?q=origami+water+bomb https://www.google.com/search?q=origami+water+bomb returns maker videos, text instructions, etc.