Jellyfish are white, floating saucer-shaped organisms with long, thin tentacles that drape into the water they live in. Despite resembling creatures, they are considered foreground objects, meaning that they reflect thrown Spears & Rubbish, and can be pushed around.
When thrown, Jellyfish flash white for about 3 seconds, delivering a powerful shock to any creatures that touch them during this period. Shocked creatures cease all function and shake violently on the ground. The intensity of the shock generally depends on the mass of the creature, with lighter ones experiencing stronger, longer shocks. Repeatedly throwing a Jellyfish to stun and dealing damage while it's unable to fight back can make killing even a large predator much easier.
Stunned creatures can't track the Slugcat, making those few seconds the perfect opportunity to hide or get away, while stunned Vultures fly away upon regaining consciousness, similarly to how they try to fly away when stabbed twice with Spears. It is also possible to utilize Jellyfish to evade Leeches, as they get caught up in the Jellyfish's tendrils.
The player is not credited for kills caused by a Jellyfish shock, unless they deal damage by other methods immediately before it. This means that the kill gives no points or Outlaw progress, and that the creature respawns the next cycle with no chance of lineaging.
In water, Jellyfish may grab onto creatures below them with their tentacles, delivering a much weaker shock.
The Slugcat can grab and hold onto Jellyfish even while they're flashing white.
Jellyfish are capable of stunning creatures even when partially eaten.
Due to the intensity of the shock depending on the mass of the creature, it completely immobilizes Rain Deer, making them fall to the ground and potentially get eaten by Worm Grass.