Player 1: The main goal here is to stop the Turrets from hitting you along the thin corridor. So you first need to get a portal on the wall with the light bridge on it and then on the wall just to the right of the stairway (that’s straight ahead of you). This will block off the turrets to the right.
Player 1: Repeat the same step as from the first part (set your light bridge barrier on the wall beside the stairs). This’ll cover the right-hand set of turrets.
Player 1: Drop down onto the bridge below you and put your first portal on the wall to your left and then do a 180 and look up at the platform just up above you. Get player 2 to follow you up here, where you both need to stand in the alcove out of the way of the turrets.
Player 2: Look for the second light bridge up near the ceiling in the middle of the room. Get a portal on the spot where it meets the wall and then fire a portal directly behind you. This’ll create a vertical barrier, protecting you from the turret’s fire.
Player 1: Replace your bridge below you with one in front of you by resting a portal on the wall panel behind you. This’ll create a bridge straight across to the other side and player 2’s vertical bridge will still be providing essential cover from those pesky turrets. Run across the bridge (with player 2 in tow) and ask them to run straight across to the other side and wait for you. Stand right in front of the vertical beam (directly facing the red plunger) and ask player 2 to remove the vertical protection from in front of you. Without hesitating, run forwards, press the button then backpedal so you’re standing directly underneath the funnel above you (allowing you to catch the round weighted ball as it drops down).
Player 1: It’s now a simple matter of carrying the ball over the water, dropping it in its designated home and leaving with player 2 by the - now very familiar - exit!