In the Hunt is Metal Slug in a submarine.
The game begins after you're given a mission to destroy the Dark Anarchy Society (D.A.S.) in what appears to be post-apocalyptic Japan, after the polar ice caps have melted. The only remaining evidence of earth society are a sunken city, replete with submerged skyscrapers, and a Japanese town built on oil rig-style platforms. The rest of your journey will take you through underwater caverns and ruins, and finally, the flooded base of the D.A.S. itself.
The downside to the game is that it feels sluggish. You just don't feel like you're moving very fast, but there are a lot of enemies around to intensify the situation and lift the game play. If you're a fan of all things Schmup then you'll love this game, but if you're picky and need your ship to move fast this isn't the one for you. So buy it for the graphics and fun game play.