(1) Take stock of your materials. Look for anything that could hold the water within itself.
(2) Arrange the materials into a shape of your choosing, that you believe will hold water. Make the shape such that you believe the water will not mind being contained within it, or perhaps even enjoy it.
(3) Fill the container with water, and invert it to test your design.
(4) Watch water escape through the cracks.
(5) Refine your design. It may not be as beautiful as the previous design, but that’s okay. This way, the water won’t escape as easily.
(6) Test it once again, and watch the water escape once more.
(7) Repeat steps 5 and 6. It is natural for water to want to escape, and to feel clever and uncontainable. But contain it you must.
(9) You have now successfully built a Watertight Container.
By Jackson Green
Demonstration can be found here.