Got out my POND LIFE book and found some more plants that you might want to
enter in google image search and see if you can find a match.
(your quickest bet would be to find a copy of POND LIFE by George K. Reid - out
of print but still may be on the shelf at your local B&N or on one of the used
book sites online - great book, my go-to book of all my 75+ reference books)

look first at water horsetail (the thick stem fits this and see if all parts of
the plant are represented in the pictures)

crowfoot - comes in yellow water crowfoot
and white water crowfoot
water marigold
water milfoil
fanwort
bladderwort
mare's tail
southern naiad
bushy pondweed
sago pondweed
horned pondweed





kathy :-)
algae primer
http://hometown.aol.com/ka30p/myhomepage/garden.html