The Methuss Mariner was hurriedly developed by Anaheim Electronics for the AEUG during the First Neo Zeon War to counter Axis' Earth drop operations and suppress enemy forces directly at the drop locations. To accomplish this, the Methuss Mariner was designed to be capable of shifting directly to aquatic combat after atmospheric entry, and fitted accordingly with underwater combat equipment. For atmospheric entry, a dedicated flying armor is attached to the bottom of the machine that can also be used as a boat after landing and can be ejected to allow diving. The back is equipped with a large hydro system and boasts high mobility underwater. A total of three stabilizers are installed in the crotch and the legs' rear armor.

The Methuss Mariner was not mass produced because the war situation had already moved to space when the pre-production machine rolled out.