Metaphyton is an agglomeration of filamentous algae that have aggregated together, aided by the platform that plants provide in shallow parts of the littoral zone, specially in slow-moving, sheltered areas. They form brownish clouds that appear to 'hang' in the water.
The clouds dissipate in open, flowing water as the algae cannot sustain their cohesion.
Here's a cloud that got draped over a stick, and was then left high and dry when the lake level was lowered for dam repairs.
It feels a lot like cotton candy. Though metaphyton clouds look pretty unappealing, they are not likely to harbor cyanobacteria as planktonic algae do.
2024's extremely hot summer has resulted in an increase in algal clouds. Metaphyton clouds usually dissipate and collapse towards the end of the summer.