Using a super-absorbing chemical compound called sodium polyacrylate, you can turn boring old H2O into a magical blob-like substance. There’s a lot of fun you can have with these water beads, including deep frying them, but watching them turn invisible when submerged is easily the best trick.
Self-billed chemist and science enthusiast Andres Tretiakov posted a brief demonstration to Twitter showing how water beads seem to turn invisible when submerged, because they have the same refractive index as the water that surrounds them. When held in hand, light is able to reflect and create visible distortions while passing through the water beads, but in a bowl filled with H2O they blend in and appear to completely disappear. Science!