Dark Water was a series of neutral side missions in Infamous. In order to stop the spread of the lethal black tar, Cole had to destroy several kegs that contained the substance. After the Reapers began pumping their black tar across the Neon, several citizens began requesting Cole to put a stop to it. To do so, he had to destroy the tar keg on the roof of a particular building. After defeating the surrounding Reapers, he would approach the tar keg, and contemplate on whether to destroy it or overload it.
Good karma: Cole would destroy the keg with Shockwave, causing tar to pour over his face, sending him into a temporary hallucination and also disabling three battery cores. However, doing this purified the water for the civilians.
Evil karma: Cole would overload the keg by shooting it with his Lightning Bolts, causing it to release more tar into the system. While this meant that Cole's health would be safe, it also meant other innocent people would continue to suffer from the contamination.