First seen in Day 203.
The Vortex Armored Turtle is the boss of the 30th floor in a dungeon made by the [Demigod of Clear Water] in the Labyrinth City Aquarium.
It appears to be a giant blue turtle stuck to the center of the room, 8 meters in length, protected by a terribly thick carapace. In addition to being possessed of a hardness comparable to dragon scales and crustaceans, it also had tens of hollowed spikes covering it, not unlike syringe needles.
The turtle attacks by siphoning water with its spikes, creating a whirlpool that draws the victim towards it, drowning it in the process before dealing the finishing blow itself.
It relies on its hard shell to fend off enemy attacks while it feeds. Combining this with the surrounding terrain, this makes for quite a hard foe.
Frankly, there is no effective way to deal with this boss.
The thick armor has the ability to nullify lightning, ice, water, heat, and physical attacks to a certain extent.
To win, you need sufficient force to crush his forehead.