Ultraseven: S1 E21 - Pursue The Undersea Base! Ultraseven
Many marine accidents of sailing ships going down one after another occurred. Kawata, who is the captain of fishing boat, Daisan Kuroshiomaru, said he saw what appears to be Battleship Yamato right before the boat sunk. Ultra Guard started investigating the ocean floor and finds out the suspect was a Robot, Ironrocks, loaded with bomb which was created by Alian Mimy using wreckage of the Battleship Yamato aimed to take away seabed resource of earth!