Technology & Combat Characteristics
The first amphibious mobile suit produced by the Earth Alliance, the GAT-X255 Forbidden Blue is a variant of the GAT-X252 Forbidden Gundam and its propulsion, sensor and weapon systems have been modified to fit its role. Although the CIWS guns and arm-mounted machine guns are unusable in water, they are retained as they can be used after the mobile suit has surfaced. The original Forbidden's plasma cannon and railguns are replaced by a phonon maser cannon and torpedo launchers, while the heavy scythe is quadrupled and changed into retractable weapons built into the shields. A trident now serves as the mobile suit's handheld weapon, and a tail extension containing multiple equipment is added to the backpack to improve Forbidden Blue's aquatic performance.
Forbidden Blue retains the Trans-Phase armor, "Geschmeidig Panzer" energy deflection armor and the ability to transform into a high-speed assault form. The primary purpose of the energy deflection armor is different from that of Forbidden Gundam, they are employed in Forbidden Blue as pressure hulls and to move through water. A total of 4 units were produced and the data obtained from these units were used in developing GAT-706S Deep Forbidden and later, GAT-707E Forbidden Vortex.
History
After ZAFT forces stole four out of five of the Gundam-type mobile suits created as part of the G Project by the Earth Alliance, the EA created three more new Gundams. One of these suits was the GAT-X252 Forbidden Gundam, which later served as the basis for a new series of underwater-use mobile suits to counter ZAFT's underwater mobile suits. The GAT-X255 Forbidden Blue was the first of these new models as well as the prototype unit. In total, four Forbidden Blues were built.
One Forbidden Blue was tested by underwater ace Jane Houston. She used it in the Second Battle of Casablanca on July 24, C.E. 71, which also marks the formal introduction of the Forbidden Blue in battle. Jane later used the Forbidden Blue during the South American War for Independence, where she initially battled against Edward Harrelson and his GAT-X133 Sword Calamity Gundam, before defecting to the USSA and used the Forbidden Blue against the Earth Alliance. Another unit was covertly transferred by Muruta Azrael to Orb Union's Sahaku family.
Data collected from the usage of Forbidden Blue were used to create the mass-production units, GAT-706S Deep Forbidden and later, GAT-707E Forbidden Vortex. Both of these mobile suits fixed a design flaw regarding the use of Geschmeidig Panzer system underwater and visually, the Forbidden Vortex is indistinguishable from the Forbidden Blue.