Revelation 16:3

3  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.

In the previous trumpet judgments, there was a similar judgment on a third of the earth. Now we see these things are taking place on the whole earth. These judgments cannot happen until the angel pours out the vial, so these are separate judgments and are not just expansions of the trumpet judgments like some writers have speculated. When the second angel pours out his vial the sea will become like the blood of a dead man and everything in it will die. This is not dark red/brown food coloring; it is a very foul toxic substance that kills every living thing with a soul in the sea.