Jellyfish anatomy
Jellyfish have no brains or internal organs, and they don’t hunt prey per se.
Nor are jellyfish hunted as prey, which could be why they have been around for so long and show no intention of going extinct. Jellyfish eat small fish and plankton, but their prey comes to them. The jellyfish will open and close its bell (head) where the mouth is and create a current. It is the current that draws the prey to the jellyfish.
The jellyfish has very long tentacles, which when rubbed against prey releases several tiny stingers that poison the prey, which can then be eaten. But because jellyfish have no brains, it doesn’t know how to distinguish prey from rocks from humans, and so on. Anything that the jellyfish’s tentacles touch will be sprayed with poisonous stingers.