Ada Chapter 1
You can sneak around if you want to make things a bit easier. It is okay to be seen by one guard – as long as you kill him fast enough not to trigger the alarm. Mutated guards won't trigger the alarm as well but will take more effort to take out.
A cat in a tub
After reaching the part where there are two guards, you can get past them by pushing the gas containers out of the way to reveal a vent underneath. Moving on, Ada will notice more guards and one near an alarm. Get behind cover and take out the two guards in the corridor, then the other one inside the room with the alarm. Going past that corridor and as soon as you take the stairs, you should find this campaign's first emblem.
Follow the path until you reach a locked, decorated room. Try to open the door to update your objective. First, head to the other room and examine the hole in the side. The view's gonna be blocked so check the other side to activate it. Peek through the hole again to see the painting transform.
To open the door, you have to turn the pedestals to make the snake in the painting. Activate the console on the door then exit. Step on the lighted panel so the armed camera gets activated and attacks your enemies.
Continue to the room and loot the items. Activate the projector to get the secret information. The whole sub will be alerted at this point so there's no use going discreet now. Fight your way through more enemies until you reach the cargo hold.
Step on the glowing panels there to activate the security cams and help you take out more enemies. There is a mounted turret in the other side of the hold. You can easily take out the enemy manning the turret by activating the floor panel. Continue past the door and operate the console to unlock the next door that leads to the next area.
Open the door then continue forth. Check behind the pillar as you turn around the corner to find another emblem. Go down to the room below and grab the Assault Shotgun by the workbench. Continue following the path and taking out enemies until you reach the ladder going to the Engine Room.
Submarine Emblem 2
Fight your way through more enemies until one of them accidentally hits a gas tank which will cause a shitstorm of problems. The next sequence is just a straightforward one; you don't have to kill all enemies along the way; just run and make your way to the escape pod.
The hull has been compromised
After this sequence, walk around a bit then use the grappling hook to pull yourself up. Water will start to fill in fast so you have to move quickly. There's another emblem that you can grab during this sequence and it's not hard to miss. Continue until you encounter an enemy. (That's the only enemy you'll encounter in this sequence) The emblem should be beside the stairs.
Submarine Emblem 3
After reaching the temporary safety of the bulkdoor, jump down then continue forth. Destroy the special BOW along the way then vault over the next doorway. Before moving forth, turn around and look in the corner behind to find this emblem. Destroy the crates here as well then backtrack to reach the ladder in the other end of the hallway.
Once there, operate the console to update your objective. You have to restore power by reaching the controls. You can explore the areas and kill more of those insect-type BOWs for more skill points but still, you'll be forced to go underwater to reach the console.
Pull the lever then dive in the water again. Don't backtrack; instead follow the vent until you surface to the other side. Dive down again and surface to reach the jammed doors. Open it up and go through another vent to reach the console.
Restoring power to a disabled sub
After activating, you'll have to answer several questions to authorize your access. During this point, more enemies will attack. Fend yourself and press the buttons as soon as available to give your answers. Once done, use your grappling hook to trigger the next scenes and to complete this chapter.
Authorizing your escape