Grendizer: Getter Robo G - Great Mazinger Kessen! Daikaijuu
Genres: Action, Sci-Fi
Type: Movie, Episodes: 1
Aired: Jul 18, 1976
Studio: Toei Animation
Source: Unknown
Rating: PG-13 - Teens 13 or older
Synopsis:
A giant sea monster known as "Dragonsaurus" has emerged from out of nowhere, terrorizing the depths of the oceans. Great Mazinger, Grendizer and the Getter Robo G team join forces to combat the new threat. But their task becomes more complicated when Dragonsaurus swallows up Boss Borot and makes its way toward Tokyo.

(Source: ANN)