Based on

Movies like Super Submarine Searaper (1991)

The Mu Empire lies deep beneath the sea near Infant Island. Mew I won the ceremony to become queen in a national sport similar to sumo, but was betrayed by a rival and banished. She was saved by the Imperial Japanese Navy's all-purpose battleship "Gokango" commanded by Colonel Kinkakuji, who set out to destroy the Mu Empire. Omanda, the guardian deity of the Mu Empire, fights back!