Yu-Lung are monstrous fish found in China; specifically, Yu Lung are described as dragons with the head and fins of a giant fish. 
The Dragon Gate for Yu-Lung
At the border between Shensi and Shansi provinces, the Yellow River meets the Dragon Gate, or the Lungman Falls.  Yu the Great cleft the Dragon Gate when creating the rivers of the world,  and to this day, Carp pass through and rise as dragons into the sky. 
The Celestial Carp, each year, compete to jump through the dangerous gate. The reward for those that succeed is immediate transformation into a dragon, Yu Lung.  An expression, Lihua Lung, means 'The Carp Becomes a Dragon,' and it is used to describe success in public exams. 
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