Apalala

In Buddhist mythology, Apalala is a water-dwelling dragon who lived near the Swat River. He was converted to Buddhism by the Buddha; this is one of the most popular legends in Buddhist lore and art. The tale is often told to Buddhist children for them to learn their happiness lies in their faith.
See more at Wikipedia.org...

[Hindu] In Buddhist legend, a water dragon (or serpent) who lived at the source of the Swat River. His conversion by Buddha is a favorite theme in Buddhist art.