The RX-79M was the outcome of an imaginative requirement for a Federation maritime mobile suit to perform an anti-shipping role. It was equipped with powerful hydrojet thrusters in its backpack that allowed great speed and maneuverability underwater, and was fitted with an array of enhanced communications systems such as a combination Active-Passive Sonar. Unique to the Gundam Submarine were its polarized beam saber and beam rifle, which functioned normally underwater as opposed to standard beam weapons which would be ineffective otherwise.
The RX-79M was known to have been deployed on December U.C. 0079 after the end of the One Year War to engage remaining maritime Zeon remnants on Earth.