Seventeen year old Mart Judson joins the crew of the yacht Seamew as its wireless operator. They are bound from San Francisco for waters off the coast of Malaysia where a treasure just might be found, if they survive an encounter with the monstrous Pirate Shark. Harry Lincoln Sayler was a newspaperman and popular youth fiction novelist. He authored several book series using a variety of pseudonyms. The Pirate Shark was published as part of his Boys' Big Game series of novels, all of which were written using the pen name Elliott Whitney.