It's supposed to be the god of the sea, keeping peace in the oceans. But one day it just went crazy and started attacking people.Fisherman
The Water Dragon was originally King Wada of the Dragon Palace, and the husband of Otohime. He transformed into the Water Dragon to protect his people from the evil that spread from Oni Island.
As the ruler of the Dragonians, he was the only one who could perform the ancient rite of transformation. He swallowed the Fox Rods while defending the Dragon Palace from the Dark Lord and was cursed, flying into a mad rage and sinking any vessel that wandered its territory, as well as devouring any swimmers. The Water Dragon, with its immense power, was the only thing that was capable of penetrating the barrier that protected Oni Island.
Amaterasu and Issun had to enter the Water Dragon's belly to retrieve the Dragon Orb, an artifact that could harness the dragon's mighty power. They succeed in retrieving the orb, but in doing so, they killed the Water Dragon. However, Wada revealed himself to them after the dragon sank to the bottom of the sea, explaining why he was drove into his fit a rage, and beckoned Amaterasu to protect the Fox Rods and to return the Dragon Orb to his wife.
When Amaterasu and Issun returned to Watcher's Cape, they found Otohime with the Dragon Orb. She used it to perform the ancient rite of transformation herself, effectively becoming the new Water Dragon and serving as a bridge to Oni Island for Amaterasu. When the Dark Lord Ninetails was slain, Otohime returned to the Dragon Palace, freeing Ryoshima Coast of the Water Dragon's rampage.
When Chibiterasu and Kurow traveled back in time to the period of Ōkami's events, they required the assistance of Otohime in order to travel to the Sage Shrine, where they could use the Knowing Jewel to learn more about Akuro. The captain of the Goryeo used his conch horn to summon the Dragonian queen. In response to their plea, Otohime transformed into the Water Dragon and agreed to transport Chibiterasu to the shrine.
Later, when Kurow and Chibiterasu were about to depart for the Moon Cave, the real Water Dragon appeared and started assaulting the Goryeo. Although Chibiterasu wanted to help defeat it, Kurow insisted that their real mission was to stop Akuro, and so they left the dragon in the hands of the ship's crew. Ultimately, the dragon proves to be much too powerful for the Goryeo, and the vessel sank to the bottom of the sea. It would go on to become the Sunken Ship nine months later.
The Water Dragon is a creature of massive scale, the length of at least three times the Goryeo. Along its gigantic body, strangely, no scales are observed, but only smooth light blue skin with dotted indigo marks are seen. The Water Dragon's head has its forehead covered in a decorative golden armor for King Wada, or just a simple crest in the case of Queen Otohime. Also, Wada's form has crimson whisker and beard, and near the heads of both Water Dragons are two short appendages (the form's substitute for their arms) lined with a crimson fin, pierced with certain decorations. On their heads, these fins are also present, raised high like a headcrest, which runs down the spine of the dragons as two parallel lines, the fin's height shortened. Interestingly, between these lines of fins, their back are shown to be like a walkway. Their tails are where the fins end, in a tipped and flat end.
The inside of the Water Dragon is very complex and equally dangerous. The digestive tract of the creature has thick walls of muscle in a blue shade, with scattered pearls, minerals and crystals inspired by dwarven mines in western fantasy. At areas in the digestive tracts where large cavities for storing water are present, then so does high, single-based flat-topped platform that resembles a bit to certain types of fungi. Around the esophagus of the Water Dragon are clusters of small fungus-like plants, as well as fleshy trees that spurts out blood when cut down. The Water Dragon has two important chambers in its body: the heartcore and the stomach. The heart of the beast is the Dragon Orb, protected by a tangling mass of nigh-indestructible tissue, can only be dissolved by the very acid of the stomach nearby, from a "corridor" lined with crystals. The stomach chamber is a deep pool for storing crimson acid, dripping from above via a gland on the ceiling. This gland, ironically, is susceptible to corrosion from the acid it secreted itself, and with enough damage dealt, it will give it, releasing the flooding acid inside, filling the stomach chamber and the heartcore with the crimson dissolving agent. The muscle walls, however, are impervious to the corrosion that would normally dissolve nigh-indestructible tissue.
- Origins of Water Dragons and Dragonians are unclear, and it is possible that Water Dragons were originally separate beings from Dragonians.
- The Water Dragons' design strongly indicates that it is based on a mixture of East Asian dragons, deep-sea fish like Pelican eel, Moray eel, and most notably the Oarfish, which is a symbol of messengers from the Ryūgū-jō hence called Messenger of Ryūgū (「リュウグウノツカイ」?; Ryūgū no Tsukai); thus being a sea dragon or a mermaid. The oarfish is also considered to be some of the animals misidentified with legendary sea serpents.
- Alongside beings such as Mizuchi, there existed dragon deities in Nippon such as the Water Dragons with the purpose of overlooking and protecting the country's lands, nature, and living things.
- Given Ōkamiden, it may be possible for a Dragonian to transform into the Water Dragon without the Dragon Orb, although they would require outside assistance, as shown when Otohime needed Chibiterasu's help to complete the rite of transformation.
- The Water Dragon is one of the few monsters to attack and harm Amaterasu, yet does not have an entry in her Bestiary list. This is probably because Amaterasu never actually engages the Water Dragon in a battle.
- After obtaining the Lucky Mallet from the Sunken Ship, it is possible for Amaterasu to avoid getting eaten by the Water Dragon by getting out of its roaming range. Amaterasu's successful escape is denoted by the soundtrack The Insane Water Dragon ceasing in volume (but still audible), played alongside Ryoshima Plains II.
- "Inside the Water Dragon "Entrance":
Although this is the inside of the Water Dragon, I had already decided that I was not going to make it all raw and meaty like the Emperor's insides. I incorporated elements of pearls and crystals, and I was also influences by the images of dwarven mines from western fantasy."—Suga (Ōkami Official Complete Works, page 200)