Though jellyfish have no brain, intelligence is built into their bodies. They appear to act on instinct to changes in the environment. Whether they have consciousness is not known.
Rhythmically moving their heads and forcing water out from their bodies, they are a jet-propelled swimming machine. Most believe that jellyfish just drift. This is not the case, They head straight for their destination, for example, usually in groups.
Somehow they know that there are others of their kind with them, though they do not have eyes. Perhaps the animal uses the Earth's magnetic field as well as ocean currents to know where they are. Some scientists have suggested they use infrasound.
✴ Science by Ty Buchanan ✴