Apocalypse Revealed # 497
497. And they have power over waters to turn them to blood. This symbolically means that people who turn away from these two essential elements falsify the Word's truths.
Waters symbolize truths (no. 50), and blood a falsification of the Word's truth (no. 379). Thus turning waters to blood symbolizes a falsifying of the Word's truths.
This has the same meaning as before, namely, that people who turn away from the two essential elements of the New Church cannot see anything but the falsities in which they are caught up, and if they use the Word to defend them, they falsify its truths.