Identification: Anybody know what this is?

It grows in bogs,swamps, and koi ponds?

 

I believe it is duckweed, not sure of a botanical name.

 

Probably Spirodela sp.

 

Maybe a type of cress, watercress, upland cress. Sorry don't know the Latin. A closeup may help.

 

I take back Spirodela sp. - did not look carefully enough to note that there are slender stems in the pic connecting the tiny leaf rosettes. Think now it may be a Callitriche sp. (Water Starwort). Compare with one pic on this page:
http://www.sci.sdsu.edu/plants/sdpls/plants/Callitriche_marginata.html

 

Duckweed is Lemna, this looks like it could be Lemna minor.

 

Eric, look carefully at top edge of plant in photo and you can clearly see stems connecting the little leaf rosettes, also some paired leaves. Duckweeds have only very fine roots, no discernible stems -- unless you count the whole plant body as a stem!