Shark

With in Ruiga's Water Release: Water Cannon Replica, Ruiga summons a shark inside the orb of water. The ninja fish can eat up to 1000 pounds of flesh or of anything. However, it appears it's only weakness id that it requires to be surrounded by water, while it is summonded, which is why Ruiga encased it in a ball of water.

Ruiga used this jutsu against Naruto Uzumaki but only Choji was caught in the bubble with the shark. Choji managed to escape being eaten at first by holding the shark's mouth open, which is a display of his incredible strength, noted by Shikamaru Nara in the Sasukeretrieval arc. Choji defeated the shark by sucking up all the water he surrounded by, causing the shark to be exposed to the air. Ruiga could not maintain the shark with a fresh supply of water from the ground, since he could not extract water out of the dry rock that surrounded him, thus resulting in the retreat of the shark.