Long before smartphones, the ultimate origami party trick was a paper square that turned into a real, throwable water balloon. Meet the Water Bomb — a model so satisfying that folders have been making it for generations.

It looks like pure magic the first time you blow into that little opening and a flat sheet pops into a firm ball. Fold a few, fill them at the sink, and you've got a backyard water fight with zero plastic and maximum nostalgia.

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