Developed by the Clarke Design Bureau based on the YF-3A GINN FEMWS, the GOOhN was ZAFT's first formally adopted aquatic mobile suit for the invasion of Earth. Designed with high speed and firepower in mind, the GOOhN was primarily used for attacking enemy vessels and coastal bases, and greatly contributed to the severing of naval supply routes in the Atlantic and Pacific Oceans.
To reduce water resistance, it had a streamlined body and by folding its legs, it could transform into a cruising mode for increased speed and traveling range underwater. Installed near its mono-eye camera was a pair of phonon maser cannons, a type of sonic weapon that could be used in water. Its arms were fitted with 7-barrel torpedo launchers, and the top of its head conceal a pair of 1030mm torpedo launchers. Finally, its fin contains a 47mm rifle dart launcher.