This is Celia's tattoo.
When I was growing up, I loved a series of children's books from Serendipity Press. I still have all them and they still make me happy. They had amazing illustrations and simple morals to the story. The logo for their publishing house was the sea serpent Serendipity, the lead character from one of the very first books. It seemed completely right to add Serendipity to my moral compass tattoo.