Ian Blumer is a former Sharkie (Sail #s 10, 182, and others), is a practicing physician, and, of greater relevance here, author of several books.
He has just published his first novel (under the pseudonym "Sidney Gale") and virtually the entirety of the book takes place on, yup, a Shark! The book is geared toward adolescents, teens, and young adults, though anyone would find it interesting and fun to read. It’s an adventure book with a twist (think, surgery on a boat in a storm).
You can find out more about Ian's book called Unto the Breach at: Unto the Breach