Note: During this mission and the next one you can earn an achievement/trophy by finding and entering a number of ammo caches hidden around the swamp. Fortunately, they are all covered in the walkthrough, so if you follow it, you will unlock it as you go!
Note: T here is also an achievement/trophy 'Diver' awarded for falling in the swamp 10 times. You can do this in this level or the following one and the number of times you jump in is cumulative, so feel free to knock it over whenever!
After the scene to start the mission, open the lockbox to the left for a Medkit, Filters and some ammo and then exit the building via the hole in the wall. Drop down to the bottom of the slope and follow the path to the left around the water. Keep an eye out for a walled compound to the right with a hole in the wall.
Make your way over to the hole in the wall and climb the stairs to the guardhouse just inside to find a cache of equipment – Gas Mask, +30 Military Grade Rounds, ammo and a Custom Weapon . Return down the stairs and look between the two tents opposite the hole in the fence to find a corpse with some ammo . To the right of this, enter the open tent behind the overturned car. Cut the trap just inside the door and check out the back of the area for a lockbox containing ammo and a Custom Weapon .
Exit the tent and turn left. Walk to the edge of the water and note the wall, truck and structure across the other side. Look slightly to the left to see a red flag. This lets you know that the ground is safe to walk on. Cross to the far side and turn right, work your way along the wall until you reach the back of the truck. There is a corpse on the ground you can loot for ammo behind it and if you disable the trap at the back, you can enter the truck to find a container with 4 Incendiary Grenades in it.
Backtrack to where you crossed the water and look back to where you came. If you look over to the right of this you will see a fuel tanker in the distance. Cross the water and work your way over to the fuel truck using the red flags and solid ground to get you there.
When you reach the fuel tanker, look in the open cargo crate on its left for a lootable corpse for a Filter . Enter the gas station and look in the right hand room to find a fuel canister. Interact with this. In the corner nearby is a lockbox containing ammo and on the counter opposite you will find Diary Note [Note 1/1] as well as a collection of Throwing Knives , a Medkit and +30 Military Grade Rounds .
Just to the left of this counter outside is a broken metal girder. You can crouch and climb this all the way to the roof. You will find a hole in the roof with a lockbox containing +60 Military Grade Rounds , there is also a dead body with some ammo and a few additional Grenades scattered around up here.
Drop down from the roof and head to the tanker again. Check out the building across the water directly behind the back of the fuel tanker. Ignore the main part of the building for now (although you can find an Incendiary Grenade here if you need one) and instead go into the opening directly across form the back of the truck to find a couple of corpses to plunder and a Grenade on a shelf to the right.
Pop back out the entrance and immediately turn left. Follow the wall here until you spot a small hole in the wall. Crouch and disarm the trap before going inside. Loot the trap for a Grenade and the stack of ammo nearby for a Claymore Mine and a Grenade . There is also a Custom Weapon here.
Backtrack to the fuel tanker and enter the side room where we checked the fuel canisters. Cross the log to the other side of the water nearby. When you reach the far end, follow the flag to the right and then take the left path marked by flags until you reach the crashed plane.
Enter the door near its tail and grab the Claymore Mines here. Work your way up to the front of the plane to find a pair of lockboxes containing ammo and just next to them, interact with the fuel canisters here. When it is safe to do so, exit the plane.
Enter the plane for a Morality Point . Head over towards the cockpit and loot the lockbox here. The crate to the right of this has some additional ammo and +30 Military Grade Rounds . Inspect the fuel canisters in the main section of fuselage. Return to the door and when it is safe to do so, exit the plane.
Turn to the right and climb the wing. Jump onto the main fuselage and walk to the end of the other wing. Drop down into the ruins here and open the lockbox for some ammo . Locate the small wooden ramp nearby, climb to the top of this and hop back across the water in the direction of the plane. Return to the wing we climbed earlier and this time use it to access a log in the water we can use to cross to the next piece of land.
Upon reaching the far side, head over to the right of the area. At the base of a dead tree here you will find a switch we can press to activate the generator here which will draw the ferry to us. Note that doing so will cause a bunch of shrimp to spawn and attack you until the ferry arrives. As such, before throwing the switch, check out the lockbox and the dead body nearby for some Filters and ammo . When you are ready, hit it.
The mutants will usually come as a shrimp and spitter shrimp combination. Try to kill off the weaker spitter first before focusing on the shrimp itself. Whilst fending off the shrimps, use the entire section of solid ground to move around to ensure that you do not get cornered. After a few waves, the generator will stop. Run over and re-activate it. As you do a giant shrimp will emerge from the water. Back away from it for a short while and a demon will appear and attack it.
Whilst they are occupied with one another, run over and jump to the raft when it comes into range. Throw the switch on board to send it to the next area. This will complete the mission.