Are these things possibly just the same material as cricket water polymer crystals?

And wouldn't cricket water gel work the same way?

However, if you're going to do that, why not just go substrateless and use actual water? I guess if you used the gel, you'd eliminate the risk of sloshing.

The polymer crystals are pretty cheap. 1 oz makes a gallon of the stuff, and costs under $5.

Theoretically could be re-used after it dries out, too.