Larvae Identification

I saw some little creatures in my pond yesterday, on the waterfall wiers.
When I got close, they 'swam' up stream and disappeared.

I managed to grab one, and looked at it under a magnifying glass. It looked
like a little tiny drafonfly, but with no wings (it was about 1/16th of an
inch long). Here come the questions:

1. Could these be mosquito larvae? I thought mosquito larvae kind of hung
upside down and breathed throught little tubes.

2. Any web page I can go to that identifies water critters?

3. Will mosquito dunks kill them, if they're not mosquitos?

Thanks.