Whilst looking closely at the seeds on an aquatic plant in my water tray, using a magnifying loupe, this amazing and unknown miniscule little blob floated by. When I saw its structure under magnification, it sparked a major inquiry and investigation into what it could be ... and it got me really enthused!
The most plausible explanation and photos I could find, was that it's likely a Bryozoan statoblast, an asexual mass of cells that is shed from the parent colony. It can remain dormant for quite some time, but is able to develop into a zooid and start a new colony when conditions become favorable. This clonal technique is unique to freshwater bryozoans.
Here is a close up of the hard core, and the little spines around its edges
And then it grows into a colony of invertebrate filter feeders like this, which can get really large and heavy, weighing several pounds.
If I hadn't been focusing on the seed details of the pondweed, I'd never have known such a thing existed. What an amazing find, and I just stumbled on it by chance! I'm so glad I stopped and investigated that seemingly innocuous blob - so exciting!