The "king of water" is a metaphorical title, and while there isn't an official ruler of the seas, the killer whale (orca) is often considered the apex predator and a dominant force in the ocean.
Killer whales are apex predators, meaning they sit at the very top of the food chain and have no natural predators. They are incredibly intelligent and hunt cooperatively in pods, using sophisticated strategies to take down prey much larger than themselves, including sharks, seals, and even other whales. Their hunting prowess and dominance in marine ecosystems often lead to the analogy of them being the "king of the water."
While various marine creatures might be considered "kings" in different contexts (e.g., the great white shark for its predatory reputation, or the blue whale for its immense size), the killer whale's intelligence, social structure, and hunting abilities place it at the top of the marine hierarchy in many people's minds.
