God had said that the wages of sin was death (Genesis 2:17), not just for people but for the whole creation God had entrusted to man’s care (Genesis 1:26–30). In line with that promise, Paul wrote that all creation was subjected to futility and enslaved to corruption (Romans 8:20–21). That even the sea would look and stink like death is a horrid expression of the righteous judgment of God on sin.
3 The second angel poured out his bowl into the sea, and it became like the blood of a corpse, and every living thing died that was in the sea.