The second plague is poured upon the sea. The sea in turn changes its chemical composition and all that lives within the sea die. The sea is described as becoming as the blood of a dead man. When a man dies his blood congeals and becomes thick reddish black and viscous. The sea will become just so as well. Many who live next to the sea and live off of what the sea produces will die as well.

This plague roughly parallels the second trumpet warning. The main difference is that this plague affects every ocean in the world and every living thing in the ocean.