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.
- Megamorph Abilities - Spits a sticky massive goo that can trap a slinger.
- 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
Jellyish slugs are much less powerful than other slugs, but they can be very useful defensively and sometimes offensively. Their Loogi move, when used on slugs, can stop them dead in their tracks, and because they don't need to hit a slug to do this, a Jellyish can attack the opponent after stopping a slug. A Loogi move is also a near guaranteed success when slingers want to stop another slinger from attacking them. Besides that, its usage is pretty limited.
- 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 due to the fact that he gets stuck in its Loogi attack.