Rust like stain on vinyl pool

[wayner]

This stain has been in my pool pretty much since it was built. Anyone know how you get this type of stain on a vinyl liner? It isn't a big deal I am just wondering how it got there. There are a couple of others as well. It is kind of the shape of a small caterpillar/worm that I get in my pool a lot.

 

[JamesW]

Possibly due to something metal getting in the pool. Try some ascorbic acid (vitamin C) to see if it comes off.