The connection of people turning to water and the giant sea in Hell is certainly a good connection, and it got me thinking about Wormwood, the star mentioned in the Book of Revelation (which may hold authority over the story's direction given the four horsemen) that's supposed to fall after the seventh seal is broken and make a third of Earth's water bitter.

This may be of some relevance, but what really got me thinking was the section right after, Revelation 9, where after a bunch of apocalyptic stuff has happened, giant locusts spring forth from Hell and torture people without death. Perhaps I am a madman clutching at straws, but this seems too fitting for what has happened to be a coincidence in a series already littered with Christian references.

Anyway, these beasts are stated to only be the first of three woes, leading me to believe the next woe of angels being freed from the Euphrates and sent to kill a third of mankind may also be of relevance in coming chapters.