Revelation 8:8

8:8 Then the second angel blew his trumpet, and something like a great mountain of burning fire was thrown into the sea. A third of the sea became blood,

Revelation 8:11

8:11 (Now the name of the star is Wormwood.) So a third of the waters became wormwood, and many people died from these waters because they were poisoned.

Revelation 9:15

9:15 Then the four angels who had been prepared for this hour, day, month, and year were set free to kill a third of humanity.

Revelation 9:18

9:18 A third of humanity was killed by these three plagues, that is, by the fire, the smoke, and the sulfur that came out of their mouths.

Revelation 16:4

16:4 Then the third angel poured out his bowl on the rivers and the springs of water, and they turned into blood.