movement on pond surface...
.8 that's great - you know what you see of course. I'm slightly puzzled in that I cannot find anything about that behaviour for leeches. I have leeches in my pond as well, and they do wriggle, although the species that I have becomes very elongated as it does so, more like a worm; in rest state it becomes more the shape in your picture. Curious!
i put some barley balls in the pond about 4 months ago...wonder if it could be a reaction off them...
As they rot they will produce gas bubbles that grow inside the balls until they escape and pop at the surface.
Sometimes gas bubbles come up from the silt at the bottom of the pond for the same reason
Knowledge is knowing that a tomato is a fruit.
Wisdom is not putting it in a fruit salad.
west central Scotland
That sounds like a possibility
Might be worth spending a wee bit of time looking to see if that's the answer.
It's a place where beautiful isn't enough of a word....
The little looping wriggly things are Midge Larvae the blackish ones that don't loop are Gnat or Mosquito Larvae.