The largest of the small
Not every single-celled life form is microscopic. Some of them can be seen with the naked eye. Some of them are, at least compared to other single-celled creatures, downright gigantic.
Here’s an article about the large amoeba that was found on the bottom of the ocean.
Here’s an article about a single celled bit of seaweed that looks like a tiny fern.
And here’s a video about why single celled organisms don’t get much larger than the examples in today’s episode.