In message , Jeff Layman
writes
On 22/08/2011 23:23, Stewart Robert Hinsley wrote:
Perhaps a garden escape/throwout, as it's not readily recognisable as a
native species.

http://www.stewart.hinsley.me.uk/Images/Dicot68a.jpg

Original photo (large)

http://www.stewart.hinsley.me.uk/Images/IMG_6191.jpg

Interesting. Some leaves appear to be orbicular, others obovate. I
wonder if it is something non-aquatic, which has just been thrown in
the pond and will float until it dies and sinks.

The stems appear to be too tangled in with the waterweed for it to have
been thrown in recently, and the foliage too fresh for it to have been
thrown in any significant time ago.
--
Stewart Robert Hinsley