The answer is: The rivers and fountains of waters became blood

Rev 16 vs 4

In the vivid and sometimes bewildering images of Revelation, the pouring out of the third vial of wrath holds a striking visual: rivers and fountains turning to blood, echoing the plagues of Egypt during Moses' time. This isn’t merely theatrics; it symbolizes judgment and cleansing through destruction—an often unsettling theme throughout scripture.

Interestingly, the people of ancient Israel had a sacrificial system reflecting life in blood as both sacred and purifying. In contrast, here, the changing of water to blood represents devastation and loss of vitality, reminding readers of life's fundamental reliance on water. Water comes to symbolize life-giving nourishment, and its contamination indicates a severe departure from divine grace.

Backtracking to ancient texts, the significance of blood is profound in the Jewish tradition, marking a means of atonement. In a way, moving from the lifesaving ability of fresh water to something deadly stands as a warning against turning one's back on moral truths.

This imagery in Revelation has made splashy pop culture appearances—from movies to literature—and highlights themes of justice, balance, and the cosmic struggle between good and evil. Moreover, it brilliantly conjures shared memories of trials faced, sometimes echoing in our daily disciplines of justice and moral reflection.

Pondering these vivid experiences of judgment reminds us of our need for restoration, emphasizing every action aligned with equity and healing; may it inspire us toward fostering living waters of goodness rather than those of wrath.