What if this turned out to be how evil plant alien people made themselves known. By mind controlling algea in a big pool.

That's what the Algae Mother wants us to think. Those of us who know the truth wait in both reverie and terror for the day her bloom smothers us all.

The president of Algae:

Antifa algae lead by the notorious hacker Four-chan

There's a short story by Stanislaw Lem (who also wrote Solaris ) about scientists who train a slime mold to be intelligent by forcing it to grow only in the shape of letters, then forcing the letters to be real words, ... and so on, until they able to have full (if slow) conversations with humans.

I just realized, it's kind of presciently like training an LLM. Story is at least 40 years old, so...