Jellyish are a common blue and green Slug found mostly in Cavern Sea Reef. It's power type is Goo blasts, and it is a water type Slug. They have a simillar body type to the Frightgeist Slug. They can defeat a Sand Angler and a Rammstone by using its Loogi attack.
- Protoform Abilities - Goo can be used for tagging or glue.
- Loogi - Spits a sticky goo that attaches to anything and is nearly impossible to remove.
- Gagtagger - Masquerades as a dud, but can attach a tracking device to an opponent when its protoform hits.
- Goo Bear - Spits a very sticky goo that stings an opponent while they try to remove it.
- Mechasplat - Leaves a sticky goo mat that traps a Mecha-Beast's feet or vehicles wheels.
- Slimeleon - Covers a slinger with goo that can change colours to create a disgusting, but highly effective, camouflage.
- The World Beneath Our Feet Part 1 (First appearance)
- The Trade
- The Slugout
- Dawn of the Slug
- A Distant Shore
- The Unbeatable Master (Loki in disguise)
- The Gentleman and the Thief
- Light as Day
- Slugterra: Ghoul from Beyond
- Slugterra: Return of the Elementals
- Slugterra: Slug Fu Showdown
- Stuff of Legend
- The Lady and the Sword
- Slugterra: Into the Shadows
- This slug does not need a torpedo shell to be shot underwater.
- Jellyish were first seen in "The World Beneath Our Feet Part 1" when Kord shot a Jellyish at Eli during Eli's first duel.
- The Fire Elemental is one of the only natural forces that can melt this slug's slime.
- Kord Says that Jellyish should be removed from Pronto's arsenal sue to the fact that he gets stuck in its Loogi attack.