Once you reach ground level near the red lake, begin searching the large concrete wall beneath the Control Tower. The Flood Access Tunnel entrance is built directly into this wall and can be difficult to notice from ARC Raiders Coins a distance.

The entrance itself has an industrial appearance and blends into the environment surprisingly well, which is one reason so many players overlook it during their raids.

How to Get the Water Sample

After locating the Flood Access Tunnel, the hard part is mostly over.

Enter the tunnel and proceed along the linear path inside. Thankfully, you do not need to explore very deep into the underground area to complete the objective.

As you continue forward, you will eventually encounter a small pool of dirty sewage water with several large pipes feeding into it. The water sample you need is connected to one of these pipes.

Look toward the left-hand side of the room and approach the pipe there. Once close enough, you will receive an interaction prompt allowing you to collect the water sample for Celeste.

After interacting with the pipe, the objective updates immediately, confirming that the sample has been secured.

Safely Extracting With the Sample

Collecting the water sample is only half the mission. Like most extraction shooter objectives, you still need to buy ARCR Coins survive and successfully leave the raid.