I’d like to suggest the swap of oyster in the place of clam, because oysters are less mobile than clams.
This leads to a funny observation: for some reason I think a worm and an oyster are obviously animals, like if you were a caveman with no notion of genetics or the tree of life and you came across either, I suspect you’d think “this thing is obviously some kind of animal.” But a sponge is not so obvious, I think, to our hypothetical caveman. I could believe a sponge is a weird plant.
I think you need at least one distinguishing feature beyond the minimal to become obviously an animal, for some reason.
When digging in sand, they are also surprisingly quick. You can see when they spout water out of their little holes in the sand, but if you don’t start digging like crazy they can easily get away.
Clamming was a surprisingly fun way to waste a morning as a kid, it is like playing at the beach with objectives. If you ever happen across somebody with a license, I suggest giving it a try.
More like "without knowledge of the particular choices made by prominent biologists".
The roots of "animal", "fungus", and "plant" are completely arbitrary; anything outside the chosen root can be called a "protist" (many marine "plants" are counted as protists nowadays).
