Johnny Starboard and the Underseas Pirates #1

Johnny Starboard and his assistant Hawkins are assigned to track down a pirate submarine after their freighter is attacked twice on secret routes. After discovering the pirate captain's plan to sink another cargo ship, Johnny pursues the vessel in a launch and manages to board the submarine. Johnny defeats the pirate captain in combat and apprehends the "water rats"—the crew responsible for the attacks—bringing them to justice.