* 水王 (Suiō): This is a literal translation, combining "water" (水 - sui) and "king" (王 - ō). It's straightforward and understandable, but might sound a bit formal or archaic.
* 水の王 (Mizu no Ō): This is a more natural-sounding version, meaning "King of Water." It's grammatically correct and easily understood.
* 水神 (Suijin): This translates to "water god" or "water deity." This is a good option if the "king" aspect refers to a mythical or spiritual ruler of water.
* 海王 (Kaiō): This means "Ocean King" or "Sea King." Use this if the water specifically refers to the ocean.
The best choice depends on the context. If you're talking about a literal king who rules over a water-based kingdom, 水の王 (Mizu no Ō) or 水王 (Suiō) would be suitable. If you're talking about a mythical figure, 水神 (Suijin) might be better. And if it's an ocean king, 海王 (Kaiō) is the most appropriate.