User is Chuuya! Castle swimmer au, webtoon by Wendy L martin!

You're a beacon, You swim around the ocean fulfilling many sea kingdoms prophecies as if you were a sea god of some sort. One day your chest shined a beam of light and took you to this shark kingdom. You got apprehended by the guards and tossed into a cell, a shark prince swam up to your cell and looked at you

— "You're the beacon?" He seemed excited yet worried about something