If you kneel down on the edge of a clear water pond and look towards the bottom, even at this time of year, you might be able to see some flattened elongated creatures slithering over the sediments, like they are levitating (above). They are planarians or flatworms. On closer inspection they have a quizzical look due to their simple eyespots or ocelli, which appear to be both looking inwards. They are relatively simple organisms, which move over a carpet of cilia and have simple guts, with a single opening, the mouth, which is sometimes placed in the middle of the body. I am trying to get some shots of water slaters and I have set up a little tank at home. Most of the time when I get some decaying leaves from my half barrel (=minipond) a few flatworms are accidentally transferred with them, and then I can take some photos of them while they climb on the walls. There appear to be several species, but yet have to find out some resources to tell them apart.
One of the most striking features of flatworms is their capacity for regeneration. If you cut them in half, each half grows the missing parts. Even a tiny part of a planarian can regenerate a complete individual.