I have another type of pool worm for you: this one is about the length of my palm (3 1/2"), black, and twice as thick as a horse's hair. It does not appear to be segmented and has no obvious head, although its "tail" twines around small objects. It moves with serpentine grace from surface to bottom of the pool--but does not resemble a snake in any discernable way.
Upon removal from the pool with a brush, vaccume, or leaf skimmer, it becomes very active--twining around an object, weaving in on itself. It dries out quickly, turning a light straw color that is difficult to see.
I have found several of these over the past three weeks, and have upped the chlorine in the water in response. Any idea what type of worm I'm finding? I don't think it is dangerous--just bothersome. The first time I found one I thought it was a tail hair from one of our horses as the back pasture meets the chainlink around the back yard and the "girls" like to congregate closest to the pool.