Isobu

The is a demon turtle that the Akatsuki assigned Tobi (with the help of Deidara) to capture.

Background
In the past, the demon turtle was imbued with an unnamed ninja from Kirigakure, later it seemed to have been extracted from its host and was set free in the wild. After that, the demon turtle lived in an ocean area and has remained uncaptured by any shinobi until Deidara and Tobi arrived. Right after the demon turtle emerged from the water, it quickly swam towards Tobi, chasing him around area. With the demon turtle distracted, Deidara molded an explosive clay fish in an attempt to capture it. It's unclear if this marked the end of the battle, as the remainder of the battle goes unseen. As the two towed the Tailed Beast to the Akatsuki's lair after the battle, Tobi gloated of bringing the demon turtle down with his special jutsu, but Deidara thought otherwise. It is later sealed in the sealing statue.

Since it was removed from its host, the demon turtle lost its intelligence and wasn't smart enough to control it own strength, which made it weaker and then was easily captured and sealed.

Abilities
What abilities this creature possesses remains unclear, as it did little to actually attack the two in its short appearance. It is clearly quite fast despite its size, as evidenced by its ability to keep up with Tobi, who was running on the water at the time.

Influence
The turtles are a common species throughout the world and stories of turtles and sea monsters have spread throughout Japan.

Its design was stated by Masashi Kishimoto to be a result of his interest in monsters, yōkai, and kaijū, mixing together various elements of those types of creatures. It's body is reminiscent of a turtle's, and the tails were modeled after shrimp.