Cnidaria

The Cnidaria (Nye-dare-e-ah) is one of the Creatures in ARK: Survival Evolved.

Behavior
Although they seem to be primarily herbivores, feeding off algae, they seem to have another favorite target: humans, and the occasional tame we bring along with. The Cnidaria may be an herbivore but this makes them act very predatory, pursuing survivors at a slow pace, but a shockingly large aggressive range, especially for a creature that’s not supposed to have any sensory organs or even a brain. Its attacks include torpor inducing stings and knocking riders off of their mounts. Do not underestimate this creature, as they can cripple almost anything, including apex predators such as Giganotosaurus and Mosasaurus, leaving them helpless as they slowly feed on them. However if one can avoid the crippling effect, it has low health and can be killed easily by players of any level. This makes the Cnidaria a common, deadly aquatic pest. They can be found alone but are most often found floating around in groups of two to seven. Wild Cnidarias do not take damage from nor show aggression towards any other fully aquatic animals unless caught in the middle of a fight between other creatures. They will react defensively if attacked by terrestrial or semi-aquatic ones.

Appearance
Cnidaria Omnimorph is a relatively large jellyfish compared to a human, with long trailing tentacles packed with venom to sedate both prey and predators. They are typically easy to spot at night and in deeper waters, as they glow a bright neon cyan color, but blend in during daylight near the surface, as they’re similar in color to the water. As they are translucent, they do not cast shadows.

Combat
This section describes how to fight against the Cnidaria.

General
Cnidaria are aggressive but have a smaller aggro radius than other aquatic predators and are very slow. The easiest way to deal with them is to just swim around them or kill them with ranged weaponry.

Do not engage the Cnidaria in a melee fight. It only takes a single Cnidaria to stunlock your mount and force you off of it, and the stunned creature effectively can't do anything while the Cnidaria slowly chips it down. Their stun attack makes it near impossible to defeat one with a melee weapon, as you are effectively stuck in their attack while they either chip away at your health or drown you. On mobile, Doedicurus does not get stunned by their attacks. Still take damage though.

Be wary of Cnidaria camouflaged into the walls of underwater caves.

Strategy
It’s best to stay out of their deadly attack, and fire at them with a bow or gun. Use their low speed to your advantage, and make sure to swim away before they get too close. SCUBA Flippers are fantastic for this purpose.

Alternatively, you can use a  to kill them without any risk, because the Basilosaurus is immune to stuns. Neither you nor your mount will be stunned or damaged, and you will not be forced off your mount. In the underwater caves, they are considered the safest option for clearing out predators because Cnidaria in caves are significantly stronger than ones in the open ocean.

Weaponry
Using a Crossbow from a raft or mount will work. If you don't have either of those, or don't want to use them, you can lure them to the shore and safely attack them from land.

can make for an effective hunter of Cnidaria due to its resistance to dismounts and large attack range.

and do not target Cnidaria.

Weakness
They are very slow and have low health and attack range.

Roles

 * Swarming Tactics/Troll: Despite being untameable and usually useless beyond harvesting their Bio Toxin, they can be utilized for the cheeky purpose of congregation. All one has to do is to take a sea creature that is immune to the electric shocks of the Cnidaria, like a or, and aggro a group of them, allowing them to follow you wherever is desired. Knowing this, one can attract sizable swarms of these jelly-fish, which can be led to another survivor's underwater base (if insufficiently protected) to harass, knock-out, and/or kill tames and survivors. This trick can also be applied in underwater combat (though only reliable in specific circumstances) when used as a small buffer to protect oneself or deter an enemy as well as stun-locking and eventually killing survivors and tames if given the chance.

Notes/Trivia

 * Dino Dossier was revealed on 09/30/15 on Steam.
 * Cnidaria is actually the name of the phylum containing all jellyfish - plus corals, anemones, and other related animals.
 * Cnidaria's genus name comes from the Greek word knide, meaning 'nettle'. Its species name Omnimorph roughly translates to "all forms". This refers to the fact that it resembles many different species of jellyfish rather than just one, as Helena points out in the dossier.
 * Despite its similarities to real-world jellies, the Ark's Cnidaria can produce electricity, along with the explosive harpoon-like stinging cells called Nematocysts or Cnidocytes shared by all animals within the phylum Cnidaria, to tranquilize prey into submision.
 * Basilosaurus, Liopleurodon and Tusoteuthis are the only creatures that won't be paralyzed by Cnidaria, however Tusoteuthis's movement speed will be decreased if it's being zapped by them.
 * The dossier states that Cnidaria could be harvested and used for "technically advanced long-distance tranquilizers", referring to the Shocking Tranquilizer Dart you are able to craft from the Bio Toxin dropped by Cnidaria.
 * v253.9 brought the Cnidaria to The Center map.
 * Interestingly, the dossier calls it a herbivore but if forcetamed it will eat meat. This is most likely an oversight of the developers.
 * The Cnidaria being a carnivore ingame is actually accurate to real life, as jellyfish (or all Cnidarians for that matter) are in fact carnivorous.