Ryujin

Ryujin (aka Ryu-o) is the dragon king, sea god, and master of serpents in Japanese mythology. With his magic jewels he is responsible for the tides, and he represents both the perils and bounty of the sea and so was especially relevant to an ancient island nation like Japan. Ryujin is often associated with or considered the same as Owatatsumi-no-kami, another water deity or Shinto kami (spirit), better known as Watatsumi. Believed to have a useful knowledge of medicine and considered the bringer of rain and thunder, Ryujin is also the patron god or ujigami of several Japanese family groups.