Revelation 16:3-4: And the second angel poured out his vial upon the sea; and it became as the blood of a dead man: and every living soul died in the sea. And the third angel poured out his vial upon the rivers and fountains of waters; and they became blood.

The second and third Vial Plagues curse the waters of the earth in the same way the first Vial Plague cursed the land with a noisome and grievous sore.¹ Doctrine and Covenants Section 61 describes this curse upon the waters, saying, "no flesh shall be safe upon the waters."² This revelation came to the Prophet Joseph Smith after William W. Phelps saw the destroyer riding on the waters of the Missouri River in 1831.³ Taken together, the first three Vial Plagues afflict the earthly elements on both land and water,⁴ before the burning begins during the fourth Vial Plague.⁵

When the second angel pours out his Vial Plague upon the sea,⁶ the water will literally become black, loathsome, and congealed⁷ like the blood⁸ of a dead man.⁹ Every living soul¹⁰ in this verse means every mortal (corruptible)¹¹ creature in the sea.¹² Sea creatures will die on a worldwide scale.¹³ This total destruction of sea life is the antitype for the limited destruction of sea life during the second trumpet plague in Revelation 8:9¹⁴ and the first Egyptian plague when Moses turned water into blood.¹⁵

Immediately after the second Vial Plague turns all seawater into blood, a third angel¹⁶ will turn the rivers and fountains of waters into blood.¹⁷ This third Vial Plague is also antitypical of the first Egyptian plague when Moses turned the waters of the Nile river into blood.¹⁸ During the second trumpet plague in Revelation 8:10-11, the rivers and fountains were bitter to the taste and sometimes lethal.¹⁹ During the third Vial Plague, by contrast, the fresh waters in all the earth will literally become blood²⁰ and every living thing that drinks this cursed water will die.²¹

Some scholars say the blood in this plague is not literal and that the inland waterways will only be contaminated.²² However, Revelation 16:5-7 clearly indicates that the blood in the rivers and fountains of waters is a literal judgment from God that will bring physical death to any wicked people who drink this deadly water.²³ The changing of water into literal blood is no more miraculous than when Jesus turned water into wine at Cana as recorded in John 2:9.

The plagues upon the physical sea, rivers, and fountains of waters are literal,²⁴ but they may also have symbolic equivalents. For example, some scholars connect the waters of the sea and rivers²⁵ with the wicked masses of people that support Modern Babylon (the Great Whore).²⁶ The Great Whore‒also known as the abominable church‒sits upon the many waters of wicked people and nations that support her in both 1 Nephi 14²⁷ and in Revelation 17:1.²⁸ With the support from her many waters, the Great Whore kills and martyrs modern saints until she becomes drunk on their blood.²⁹ When this occurs, she will be destroyed by drinking her own blood as though it is a sweet wine.³⁰ The sweet wine (blood) of her own fornication³¹ will symbolically bring death to the Great Whore,³² just as the blood-waters of the second and third Vial Plagues will literally bring death to the many waters of wicked people that support the Great Whore.