Jellybob (Donkey Kong Country Returns)
From the Super Mario Wiki
Jellybobs are jellyfish enemies that appear in Donkey Kong Country Returns and Donkey Kong Country Returns 3D. Jellybobs are based on jellyfish, with an entirely trans-blue color with flat, bulb-shaped heads and wiry tentacles coming out of the ends of their bodies.
Jellybobs are minor enemies who only appear in the Beach levels, where they often bob up and down the gaps between the platforms. Jellybobs can unleash electricity and even surround themselves with it. If Donkey and Diddy Kong get in contact with a Jellybob, they get electrocuted. The Kongs can only defeat a Jellybob by throwing a barrel at it, otherwise they must avoid them.