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. (Summary by Brian Fullen)