Diatoms are fossilized creatures... DE is basically pulverized stone. It works to kill bugs because it is very, very sharp... think like crushed diamonds but not as expensive. It works by scraping the waxy coating off the exoskeletons of the bugs thereby letting them desicate (dry out - picture the mummy in the movie sucking the life out of a human). In a wet environment, obviously that won't happen. That's also why it's NOT a good idea to breath in the dust, even from food grade DE. Like breathing in volcanic ash... forms cement in the lungs while cutting tissue
As for being a drying agent, how much moisture can a rock absorb? Actually it's not absorbing anything, it's increasing the surface area/structure that the moisture has to coat, thereby giving the impression of absorption. Essentially, you're making mud and would get as much "absorption" by adding plain dirt.
If it's actually drying that you want, using something that actually absorbs moisture would be far better. Justsayin... If you believe it works for you, that's really all that matters, right?
