Marine was a secret camouflage exclusive to the Wii version of Call of Duty: Modern Warfare 3. However on November 2nd 2012 it was made available on 360, PS3, and PC for all.
It is unlocked after prestiging once, along with the Winter Camouflage (Wii). The pattern is a pixelated pattern, similar to the "Urban Digital" pattern, and "Digital Camouflages" of past Modern Warfare titles.
Also once the player gets Overkill Pro, their second primary can use this camo, the same goes for the Winter camo, which has to be obtained under the same circumstances.