Sounds like you have a Horsehair worm. They are named that because they used to be found pretty often in horse 's water troughs. People who were unfamiliar with science thought it was a horsehair come to life.

I tried to copy a photo but it doesn't work for some reason. See the link for a good representation of what I remember seeing when I was a kid. Rather alarming but harmless to vertebrates including humans. They are often found in water, even very small amounts of water. They prey on larger insects like grasshoppers, living inside the insect until it dies. It exits the dead insect and then lays it's eggs. Several sites have a good description of the life cycle.

Here is a link that might be useful: The worm.