Cyrus The Unsinkable Sea Serpent
Though Cyrus may look big & scary, really he doesn't have a mean bone in his body. But sometimes just wandering the sea doing nothing gets a little boring... Maybe being a real monster would be more fun? When a shark accuses Cyrus of cowardice because he won't sink any ships, the kindly sea serpent almost succumbs to peer pressure, but learns at last to be himself. Paperback book by Bill Peet.