Have you ever heard of a fish named remora, with an oval-shaped sucker on its head? At the very beginning of this book, Boca the remora was caught by fishermen who took advantage its sucker to capture bigger fish. Later, with the help of Frogboy, a 12-year-old boy who was good at diving, Boca restored freedom and agreed to travel around with Frogboy, introducing the underwater world to him. Along their journey, they made lots of friends, learned more about those renowned names, such as sea cucumber and shark, and got themselves familiar with those weird ones, such as lantern fish and sparkler fish. They even had a narrow escape from many dangerous situations. Does mermaid really exist? How Frogboy wielded his wisdom to fight against poachers? Want to know the answers? Join Frogboy and off your underwater adventure.