So here's Diver from the Seawings from Wings of Fire series.
He has no extraordinary story on him, living a happy underwater life and rarely leaving the Sea Kingdom. He's not a member of the Royal Family - his great-grandfather was a Prince though and the markings on his wings are just a result of a recessive gene that manifestated itself for some reason. He's a great singer though - unfortunately in Aquatic only. And his favourite snack are rare and elusive breadfish*.

As for the design, I was trying to work out the way Seawings' double respiratory system could work. While breathing air, the nostrils as inlet are enough, but in water they would provide too little flow through the gills, so I went for the shark model, but supported by muscle work (so the dragon doesn't have to stay in motion to keep itself from drowning). I made the whole body covered with smooth fish scales - their bodies are non-streamline enough that they don't need big, rough plates. This makes the glowing spots possible too, since fish scales are transparent. And I was trying to make something sensible with the facial-features - at first I was thinking about removing them completely since I don't find the "official" design "appendices" appealing nor useful, but then I thought about lionfish and all it's strange feathery features and ended up adding even some more. Also sorry for the great-grandfather story, but I needed a reason for him to have the royal markings and didn't want to make another Prince (there's far too many OCs with royal titles).

* After seeing the picture my husband said it's a nice fish-dragon, but I should add a breadfish somewhere... God, what am I doing with my life? -.-