Atragon

Atragon (海底軍艦, 1963) — watch online on iFILM — is a Toho science-fiction film from Ishiro Honda, the director who had made Godzilla nine years earlier.

A sunken empire strikes back. Mu, a civilization last seen above water twelve thousand years ago, resurfaces with an ultimatum: surrender or be destroyed. The nations of the world scramble — but the only weapon that might matter sits in a secret dry dock, the Atragon, a flying atomic submarine built by a Japanese naval officer who ended the war without surrendering. He built it for Japan alone. Then Mu kidnaps his goddaughter, and the calculation changes.

Special effects master Eiji Tsuburaya put a sea serpent named Manda into the ocean battle — the same Tsuburaya who had already invented Godzilla. The film takes its own premise completely straight, and the Toho model work holds. Stream Atragon (1963) on iFILM.