Revelation 8:8

And the second angel blew his trumpet, and something like a great mountain burning with fire was hurled into the sea; and a third part of the sea became blood;

Revelation 11:6

These have power to shut heaven so that it does not rain in the days of their prophecy; and have power over waters to turn them to blood, and to smite the earth with all plagues, as often as they will.

Revelation 16:3-6

And the second angel poured out his bowl upon the sea; and it became blood, like the blood of a corpse, and every living creature died??verything in the sea.

Treasury of Scripture Knowledge

Summary

Thus saith the LORD, In this thou shalt know that I am the LORD: behold, I will smite with the rod that is in mine hand upon the waters which are in the river, and they shall be turned to blood.

Bible References

And they

Revelation 8:8
And the second angel blew his trumpet, and something like a great mountain burning with fire was hurled into the sea; and a third part of the sea became blood;
Revelation 16:3
And the second angel poured out his bowl upon the sea; and it became blood, like the blood of a corpse, and every living creature died??verything in the sea.