Even without a brain - or even any form of bones for that matter - they are fascinating creatures. They emit a strange glow and can be seen even in the darkest depths of the Tibian seas, which also makes them a target for many of the larger inhabitants of the deep. Over time they developed a strong sense of danger and will flee as soon as anything other than their reflection approaches.
Was implemented at the Winter Update 2011.
Damage Taken From Elements
A jellyfish attacks in melee range.
Just kill them to make sure they're not breaking your shielding while attacking harder monsters.