These creatures evolved from simpler organisms like jellyfish.
"A huge jellyfish! It was hovering in the water.
It hurts when a jellyfish stings you.
There are jellyfish out there today, so watch out.
If you go swimming, watch out for jellyfish ‐ they can sting you!
Mark is a jellyfish so he won't be able to do twenty push ups.
... could say," Imagine a jellyfish waltzing in a library...