The Jellofish is a friend in Tap Tap Fish: Abyssrium. Its name is a play on Jell-o, a popular gelatin snack. Its body looks like a Jello mold and gradients from red to orange. It flaps its jelly-like tendrils in a very fast and erratic fashion. It's available during the First Anniversary Event of Summer 2017.
The Jellofish costs 3.000 Cake and requires you to have already collected 30 event fish.