Revelation 16:3 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.
4 And the third angel poured out his vial upon the rivers and fountains of waters; and they became blood.
5 And I heard the angel of the waters say, Thou art righteous, O Lord, which art, and wast, and shalt be, because thou hast judged thus.
6 For they have shed the blood of saints and prophets, and thou hast given them blood to drink; for they are worthy.
7 And I heard another out of the altar say, Even so, Lord God Almighty, true and righteous are thy judgments.
As the vials continue to flow the second one is poured out on the sea and it turns to blood. Remember earlier only part of the sea was turned to blood but now the entire oceans are blood and everything in them dies. Imagine the stench that is create by all the dead sea life, also the disease that could easily be create by it . The next vial comes right along with this one and turns all the rivers and springs to blood leaving it almost to have water to drink which is a necessity to life itself. Because all those through the ages have shed the blood of the saints they now have nothing but blood to drink. No doubt there is going to be a lot of death caused by theses two vials but the angels praise God and call Him righteous because this is the judgement God and promised His people. It is today God’s will that all be saved and none be lost but that is for today and not the second half of the tribulation because these people have made their choice. And Gods judgments are true and righteous.