Ok you turn off the electricty at the switch box, behind the door, then turn off the pumps at the big switch on the walkway above the water, save your game.
Ok after about 5 seconds the light will turn green, hit the switch to turn it on, run to the left of the switch and jump off, swim underwater towords the pump at the T intersection swim right, which will lead you up and to the exit, kinda of a black door in the pipe.
Now you must do this very fast, once you flip the switch on and start to run, turn on Celerity if you have it.
