Water marbles, those strange gooey little beads you see in the dollar store, are not only fun to play with, but make for some pretty interesting science experiments too.

Water marbles start out as small, hard beads but when soaked for a few hours, can absorb 300 times their own weight in water (because of the hyper-absorbent polymer they're composed of). After they soak, they're 99 percent water, and take on some curious properties — like rapidly cooling molten aluminum.

Over the course of six months, YouTubers TheBackyardScientist and Mark Rober stockpiled water marbles ordered en masse to fill a pool with the things. That's 25 million marbles weighing in at 1,600 pounds.

It all started because Mark wanted to answer the question, "What will happen if you jump into a pool of the things?" Will you sink halfway? Or could you fall all the way to the bottom of the pool? And it all ended with a ridiculous couple of videos.

In the first video, Mark explains the science behind the buoyancy of the marbles, and mostly fooling around in the pool. Who can blame him?

The Backyard Scientist's video is all about blasting the marbles with dry ice bombs, fireworks, and other rad "science" experiments. We're unsure what he was trying to prove, but anything looks good in slow motion, so we're not complaining.

And in case you're wondering, The Backyard Scientist's parents were very upset when they found all of the marbles in their pool.