What is this odd snake-like, um... thing?

Outside my door is this small dish that has collected some rain water. Today I noticed that something is swimming in it, apparently trapped inside. It’s about 6" long, yet it appears to be no more than a thick black hair, or very thin string. It appears to be about a quarter of the diameter of a strand of spaghetti. It moves quicky through the water like a snake. I can’t make out heads or tails - literally.

Any ideas?

Horsehair worm

Yep - that’s it. Thanks.

Goa’uld larvae?