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

Rev 16 vs 4

When the third vial of wrath is unleashed in Revelation, it brings a dramatic transformation to the earth's waters. Rivers and fountains, which symbolize the lifeblood of nature, become like blood. This vivid imagery serves a dual purpose—both a punishment and a significant spiritual representation.

We see this act echoed earlier in Exodus, when the Nile River turned into blood, signaling divine authority over the powers of Egypt. This connection to events of the past is fascinating because it underscores how Revelation taps into historical narratives to convey larger truths. The red liquid isn’t merely a spectacle; it engages deep themes of justice, purification, and perhaps the hypocrisy found in human disregard for creation.

In a culture heavily reliant on water for sustenance, this vial symbolizes a complete disruption. It serves as a grim reminder of the consequences of humanity's actions and, perhaps, their relationship with the divine. Each "vial" can be perceived as not just punishment, but also as calls for repentance and reconnection with righteousness.

Interestingly, many ancient cultures revered water systems and considered them sacred. When Revelation subverts that sanctity, it can also be seen as a call to reconsider our stewardship of the earth. Take note, in our own modern context, how vital clean water is to our communities, underlying a continuous lesson about respect and responsibility towards our planet. This powerfully invites us to reflect on our ecological practices today!