The Chinese Gwanyin and Korean Gwanum, both local variations of Avalokiteśvara, are often depicted standing serenely on a dragon's back, coiled through a churning sea.
For the sake of energy and time conservation, here is the story copied from Wikipedia;
...a distressing event happened in the South China Sea. The sons of one of the Dragon Kings (a ruler-god of the sea) was caught by a fisherman while taking the form of a fish. Being stuck on land, he was unable to transform back into his dragon form. His father, despite being a mighty Dragon King, was unable to do anything while his son was on land. Distressed, the son called out to all of Heaven and Earth.
Hearing this cry, Guanyin quickly sent Shan Tsai to recover the fish and gave him all the money she had. The fish at this point was about to be sold in the market. It was causing quite a stir as it was alive hours after being caught. This drew a much larger crowd than usual at the market. Many people decided that this prodigious situation meant that eating the fish would grant them immortality, and so all present wanted to buy the fish. Soon a bidding war started, and Shan Tsai was easily outbid.
Shan Tsai begged the fish seller to spare the life of the fish. The crowd, now angry at someone so daring, was about to prise him away from the fish when Guanyin projected her voice from far away, saying "A life should definitely belong to one who tries to save it, not one who tries to take it."
The crowd, realising their shameful actions and desire, dispersed. Shan Tsai brought the fish back to Guanyin, who promptly returned it to the sea. There the fish transformed back to a dragon and returned home. Paintings of Guanyin today sometimes portray her holding a fish basket, which represents the aforementioned tale.
But the story does not end there. As a reward for Guanyin saving his son, the Dragon King sent his granddaughter, a girl called Lung Nü ("dragon girl"), to present Guanyin with the Pearl of Light. The Pearl of Light was a precious jewel owned by the Dragon King that constantly shone. Lung Nü, overwhelmed by the presence of Guanyin, asked to be her disciple so that she might study the Buddha Dharma. Guanyin accepted her offer with just one request: that Lung Nü be the new owner of the Pearl of Light.