According to Japanese mythology, Dragon King has the ability to shapeshift into human form and live in an underwater crystal palace. It can also manipulate the weather and bring rainfall. Japanese people build this kind of boat and use it in some festivals. This is also a 3D modeling test given by a Japanese animation and game company called NamedAfterBy Co., Ltd, in Tokyo, where I worked as an 3D animator later there for half a year.
After researching on the real world images, I drew this sketch.