Trying to identify long worm

[Đẹp Trai]

Hello,

I am trying to identify an organism, apparently a long thin worm, that I recently saw in a very small creek in western USA.  I estimate that it was approximately 2-3mm in width and at least 60cm in length or perhaps even >1m (hard to say as I never saw it completely uncoiled).  It seemed to be round and completely uniform in width over the entire length and perhaps was finely segmented but I'm not sure, perhaps not.  It seemed to writhe a little in the water, and when I removed it with a stick it was clearly alive, coiling itself up into tight curls; when I replaced it into the water it uncoiled again.  I was in a hurry so I didn't get a good photo but I did snap one which doesn't show the complete worm, only partial:
http://meta-dynamic.com/pdocs/long-worm.html

There are many wild animals in the area, including large mammals such as bison, bear, wolves, deer, antelope, so of course parasite is a possibility.  I've no clue myself, any ideas?

Thanks in advance,
-- Đẹp

[Đẹp Trai]

Update: my suspicions have fallen on nematomorpha, "horsehair worm."

[John Martin]

I think if it appears segmented it would be an annelid of some type rather than a nematode, but its hard to say.   You might try checking with your local zoo, they might be more able to help you figure out what you've found.