A few days ago, I stepped on a puddle that was over concrete, it was all green and mossy, and almost fell down. It was the most slippery thing I've ever seen.

Aside from the embarassment, it left me puzzled. Why that so slippery? What is the fricction coefficient there? Is it the thing or is it slippery because of some substance?

The idea here is to Reserch that, and find out if you can make a lubricant out of it.