The Earth-made Spazer No. 2, developed by Dr. Umon Genzo.

Like other Earth-made Spazers, it is powered by photons, the same as Grendizer, and its armor is made of the same Super Alloy New Z as Great Mazinger.

It was created to increase Grendizer's underwater combat capabilities, and when combined with the Marine Spazer, it can travel underwater at 40 knots. Grendizer's energy consumption doubles when underwater, but energy can be replenished by combining with the Marine Spazer. Incidentally, it can also travel underwater and in the air on its own.

While the Marine Spazer was developed for underwater combat, it has the drawback of only being able to dive to a depth of 400 meters. For this reason, a separate machine called the Ultra Submarine must be used for deep-sea combat.

Unlike other Earth-made Spazers, only Hikaru Makiba pilots it in the film.