The Waters of Life

 is a Fallout 3 quest. It is also an Xbox 360 achievement.

The quest is about reactivating the abandoned Project Purity, a water filtering facility set up 19 years before at Jefferson Memorial.

James quotes the following Bible passage in the tutorial: "I am Alpha and Omega, the beginning and the end. I will give unto him that is athirst of the fountain of the water of life freely."

During the Quest you must first clear out the area for the scientists (Dr li and her fellow scientists, and your dad)

After clearing the basement, the museum/gift shop and the rotunda, your father sends you on some routine maintainence missions, to bring the project back online. after repairing the fuses and draining some of the flooding, your father sends you off to remove some blockages in a pipe.

During this time the Enclave attacks. You must fight your way through a few Enclave soldiers in power armor to reach your father. When you arrive at the control room, Dr li is locked out of the main area, while a scientist, your father, an Enclave officer and 2 Enclave soldiers are locked in. You are forced to watch the officer execute the scientist to get your Dad to give up control of the project and help Enclave scientists get it online. Your father admits defeat and heads over to the controls. Your father promptly floods the area with radiation, killing the Enclave soldiers and officer. You see your father one last time at the glass, before he says "run...." and collapses dead.

you must then escort Dr li and the other alive scientists (they dont have to survive) through the sewers via an emergency secret exit. inside you wil face feral ghouls, a tougher version of the aforementioned ghouls and plenty of Enclave soldiers.

Once at the end of the tunnel, you arrive at the Brotherhood of Steel Citadel, and complete the quest. This quest also unlocks the ability to train in power armor, and you have 24 hours (not sure if this is true, I found the distress signal long after I first visited the Citadel) to visit vault 101 to complete a quest inside there (picking up a bobblehead that can be missed at the start of the game)