Ryujin is God which lives in the royal palace in the dragon’s world. People worship Ryujin as "God of water, or marine God." It is said that a tornado is "a scene which Ryujin goes up to Heaven." 

A place for you to wash a hand is located at the entrance of temples and shrines. Ryujin is there in many cases. Moreover, Ryujin is in "the place which prays for rain", or "the place which prays for the safety of a voyage." Furthermore, since it is said that Ryujin brings people wealth, Ryujin is in "the pillar and ceiling picture of a shrine, fusuma painting, openwork grating, etc." 

When you visit to temples and shrines in Japan, you can enjoy the search for Ryujin there. You will surely be able to meet with wonderful Ryujin there.