Mu Submarine

The Mu Submarine is a submarine created by Toho that appeared in the 1963 film, Atragon.

Atragon
The Mu Submarines were the standard transportation of Mu Agents from Mu to the mainland. They were also used to attack ships from below. They could dive to extreme depths, causing the Red Satan, which was tailing it, to explode. After the destruction of Mu, two submarines escaped, but they were frozen by the Gotengo's Zero Cannon.