Yubei, a stunt actress, accidentally fell into the sea into the territory of the mersharks, the enemy of humans. To survive, she bluffed that she was a human princess. In order to meet the human emperor and negotiate for a ban on the slaughtering of ocean life, the mershark prince who has been cut off from communications with the land dwellers for hundreds of years held a sensational underwater "marriage" with the "human princess"