Going back to the extraction zone
1 - starting area
2 - destination
3 - boat
4 - waterfall
5 - river blockade
As you've probably noticed, you will have to go back all the way to the southern area of this map. Thankfully, only the first part of your journey is going to be difficult. Start off by leaving the research dome. You will have to jump over several objects along the way. It's dark outside, so it's going to be easier to outrun enemy units (smaller field of view). Sadly, you may have some problems spotting them.
You will have to make a very important decision here. Your first objective will be to go back to the river which is located to the south of this base. You can try and stay in the shadows or you can fight your way through enemy checkpoints. I would recommend choosing a more direct approach. As a result, head on to a nearby truck (screen).
The most important thing here will be to keep moving in order to prevent the truck from receiving too much damage. Also, you can't hit any of the nearby objects, because that would only slow you down. Head on forward. Turn left and then right. You will have to go through your first checkpoint (screen). Keep heading south and don't leave the main road.
You will come across an enemy humvee in just a few seconds. You could try and fire a few rounds at it, however it's more important to keep moving, because your truck can't withstand too much damage. Keep moving south. Exit the truck once you've reached a small junction (screen). You've been here before, so you should be familiar with the surroundings.
Activate your cloaking device as soon as you've left the truck. After that, hide somewhere in the bushes. If you're lucky, you won't be attacked by anyone. Now you must start moving towards the river. Ignore enemy soldiers, because they won't follow you (they will probably stop near the truck). Once you're close enough to the river, turn right. This area should be safe.
Your next task will be to find a small shack. There's a boat here and you will be given an opportunity of using it. The easiest way to reach the boat would be to start swimming towards it. Enter the boat and start moving forward. Sadly, you'll come across a waterfall in just a few seconds. Don't even think about staying inside the boat. Instead, leave it and carefully approach the waterfall.