While looking into my pond this morning I noticed a really weird-shaped thing moving slowly across the bottom. Hunched over like a vulture, I tried to make out what was head and what body but it kept changing its shape slightly. I was really puzzled and must have spent a good five minutes watching it before I realised what it was - the shadow of a small clump of duckweed that was drifting about on the surface! What an idiot I am! :-[