I thought it was horsetail?
http://i27.photobucket.com/albums/c180/beckyandy/tadpoles2038.jpg
http://i27.photobucket.com/albums/c180/beckyandy/tadpoles2039.jpg
http://i27.photobucket.com/albums/c180/beckyandy/tadpoles2040.jpg
It is a horsetail, of which there are several native species. Looks to by water horsetail's fertile stems, but may be Dutch rush (also an Equisetum), or may be a hybrid, which they do frequently.
Thanks, I thought it was but googled and other wern`t plain but more like asparagus and fluffy!
Water horsetail often doesn't have any branches, even on sterile stems. Dutch rush isn't usually found in water but does like wet ground and never has branches and (if I remember rightly) all stems are fertile.
Giant horsetail is one to look out for, very impressive but can be a bit rampant!
Equisetum palustre
It's not marsh horsetail (Equisetum palustre), which has branches, fewer ridges and the nodes have black teeth with a broad white edge.