Reach the water treatment plant | Mission 3 - American Consumption Splinter Cell: Blacklist Guide

A reconnaissance drone

Start exploring the partially-flooded tunnels, follow the linear path and do not fear any confrontation with any of the enemies for now. After you reach the end-part of the tunnels, take the ladder and climb up the stairs. Keep vigilant here, because the corridor that you are about to step into is patrolled by a reconnaissance drone. For obvious reasons, you need to avoid ending up in front of the drone and being spotted, which will result in an alarm being raised. Fortunately, the first machine moves in a straight line, which makes it easier to avoid it.

The walk along the upper catwalks

Right after you enter the location guarded by terrorists, approach the large pipe in the middle of the corridor and pull up to reach the overhead catwalks attached to it. Walk along the catwalks but, do not ignore the enemies below entirely, they can still spot you. A good way to prevent being spotted is to use suppressed arms to destroy light sources. If you have already run out of ammo then, before you go under every glow tube, check the area carefully.

A exit from the corridor guarded by terrorists

After you reach the end part of the catwalks, turn left and wait for the enemy patrolling the area under Fisher to go the opposite direction. Additionally, make sure that the reconnaissance drone isn't anywhere around and, only then, drop down. Squeeze past the drone operator and leave this location.

Note- If the drone operator keeps detecting Fisher, you need to divert his attention beforehand. Do this by encouraging him to leave his post, using your gadgets.

After you enter a huge shaft, do not use the stairs to the right and turn left to climb up the ladder. Grab onto the horizontal pipe and shimmy to the right. Then, go up, which will allow you to reach the Dead Drop shown in the above screenshot. Collect the item (10 thousand dollars), and go towards the upper levels after you do that. Watch out towards the end, because there is a single guard around. Wait for the enemy to start walking towards the balustrade to the left and squeeze past the terrorist carefully. Turn right to reach the water treatment plant vicinities.

Additional tips for the Panther/Attack playing style: it is worth knowing that destroying a reconnaissance drone with a suppressed weapon doesn't equal raising the alarm. Still, you will gain nothing because the operator will send another machine.