Fighting Undersea Commandos #4

In "Destroy Target 'X'!", six U.S. Navy frogmen under Lieutenant Riddell board a submarine with sealed orders to complete a dangerous mission observed by North Korean civilians near the restricted zones of Chongeb, Linwo, and Sanshee. A Red agent known as the Black Shark threatens to kill Barnes and other technicians unless demolition experiments are surrendered, leading to sabotage and deaths among the team. Lieutenant Hansen must use the frogmen squad to stage the demolition of the experiments while hunting the Black Shark off the Korean coast.