Coins are supposed to sink. When you toss 'em in a fountain, they drop right down to the bottom, right? Not always. There's a trick that can actually make metal coins float, and it's totally trippy to see. You carefully level the coin (which needs to be made of aluminium and not zinc) onto the surface of the water with a paper clip, and then slide the paper clip away. Boom! You've just become a sorcerer. The metal coin is floating.
The surface tension of the water is just strong enough to keep the aluminium coin afloat if you're know what you're doing. Grant Thompson illustrates how it's happening with coins, paper clips, dish soap, and pepper flakes in the video below.