Lycopodium powder is a collection of spores from a plant called club moss, and it is not only incredibly hydrophobic, but also very flammable.
Spores are essentially single cells that contain massive stores of energy in order to help receptor plants grow further. This power behaves very oddly on water, so much so that you can light water on fire when the power is mixed with it. Check out the interesting video below.
Since these spores are only single cells, it also means they are quite light. The reason they are hydrophobic is to keep the powder as light as possible so it can travel by the slightest of breezes.
If you were wondering if you could purchase this powder, of course, Amazon sells it. If you want to buy some super-hydrophobic flammable plant spores, you can do so through this link.
[Image Source: Steve Mould]