Gabe Logan: "Teresa, what the hell's going on? The entire dam's shaking..."
Teresa Lipan: "Enemy comm is going crazy. Dam engineers are reporting structural instabilities."
Al-jamil Thug: "It will collapse at any moment! We must go! We must go now-"
Teresa Lipan: "I'm updating your tactical plan for immediate extraction."
Gabe Logan: "Negative. Bitar's still got the bomb, and I'm not leaving without Lian. Logan out."
Dive into the water at the mission's start, and surface behind the turbine guard. Approach him silently and smash his head into the panel he's working on. Search this place for a ladder you can climb. Do so and turn around to see three turbine cores. Shoot them (I'm assuming you retained the Mark 23 SD from the previous level) and then return to the first floor.
Silently enter the door near you (DON'T kick it!) and move further in without letting the enemies see you to trigger a conversation. Immediately move back out and climb the ladder again. An enemy will eventually enter the area you're in. Drop down and kill him. Go back through the doorway you entered earlier and snap to the wall directly in front. A lone guard is wandering up and down near you, behind the gate. Snipe him with a silenced headshot and head towards the path that goes to a pool.
Two guards are here, an active and a stationery. Wait for the former to approach and nail him. If the second notices anything, he'll enter the pool and wander what it was. Drop him when he does. If he didn't see anything, you can snipe him from a distance.
Go through the pool and you'll come to a series of doors. Wait at the furthest one and you'll see two patrols. Again, one is moving and the second passive. When the first has his back to you, enter this turbine room and nail him. The latter should be busy, so smash his head into the control panel.
Return to the pool area and go back to dry land. You'll notice a ladder to the east. Climb this and wait for the patrol on the opposite side to move up the ramp. When he does, drop down on the other side and kill him. Continue up the ramp and a door will be ahead. Enter it silently and a couple of guards will be talking near you. Snap to the wall close to them and use a gas dart to nuke them. Going through the next door will bring you to another enemy. Shove his head into the control panel with a melee attack and interact with this. Destroy the three turbine cores to complete this objective.
Return to the doorway that accesses this area. A few guards will intercept you, so drop them. Going back to the ramp will spawn another group. You can either take them out or climb the ladder to your left to use an AZL which allows you to bypass them. Whatever you choose, there's an ammo box on the zip line platform so replenish your weapons before proceeding.
If you elected to use the AZL, you'll land on a platform. If you took out the enemies, the coast will be clear. You can continue down the slope and ascend a ladder to arrive on the same platform. Drop down the ladder on the far end to arrive back at the pool area. A swarm of guards will confront you so nail them. Watch out for those with the Desert pistols.
With this wave neutralised, you can head into the pool and hit the elevator switch. A duo will now spawn, and they're wearing AS armour. If you've played the previous game, you'll be familiar with how to kill them. Otherwise, you must disable them with an electric or explosive attack and shoot their backpacks. There's a switch that activates the current in the pool, temporarily stunning these guys. Go for the back shots and drain their health. If they arrive on dry ground, use your EDT darts and taser instead. When they're dead, get the elevator access card and their G11's. Approach the elevator they used to approach you and the mission will end.
- On your way to disable the second turbine, there is a ladder that goes up and around a huge pipe. Descend to the other side and climb the ladder at the opposite end, the hidden evidence is lying next to an ammo box.
- On your way to push the elevator button, before you jump into the pool, look for a small corner with pipes in the middle. Behind the pipe is a hidden evidence.
- Before you go up the elevator, go toward the door on the end of the pool room. Follow it and then jump to the big pool. At the bottom of the pool, there is a dead body and a hidden evidence. Use EDSU to help to spot the body.
- After the above evidence (#3), rise out of the water to get a breather and use your EDSU goggles. Dive back and look for gratings. Shoot the mines that surround the gratings and continue to the next pool room. Surface and get the hidden evidence that is lying next to the machinery/RPK weapon box.