The Enemy Below is the twentieth mission of Metal Slug: 2nd Mission. Only Red Eye has access to this stage.
After Red Eye gets confirmation of her info, she takes a ferry to the North Harbor. However, a large Rebel sub comes by to impede progress. Red Eye must use a crank to drop barrels of oil on top of the sub. The Sub slowly moves from right to left, so Red Eye has to time her drops. Every time the Sub passes by, five missiles are thrown to Red Eye which she has to dodge or shoot them.
After a couple of barrels hits the Sub, Red Eye goes on top of the ferry and engages in an ambush of Flying Rebels and Rebel Divers. The ferry's turret gets bombed once the ambush finishes. A second helping of bombs results in another ambush, this time consisting of Bazooka Soldiers and a R-Shobu.
|This is the local agent. Come in, Red Eye! It’s urgent, over. Red Eye!|
|Unbelievable! That agent’s just plain rude! Dismissing my info like that. “Is this for real?” What a putz! PF Squad! HA! Bunch of… Yeah? This is Red Eye. Over?|
|Say what? IHQ has new orders for me, do they? Analysis shows alien life-forms are confirmed. They’re in league with the rebels! It seems there heading into space with them, eh? The base is to the northeast? Go by boat to the North Harbor. My mission’s to stop the launch of the rocket, eh?|
|I knew my mission was right! Bio weapons my patootie! Aliens?! Things are really getting spooky. OK! I can’t lose out to the likes of PF Squad!|
Completing this mission proceeds to Mission 24 (The Ice Queen).