512. And the third part of the sea became blood.- That this signifies, that everything therein became the falsity of evil, is evident from the signification of the third part, which denotes all (see above, n. 506); and from the signification of the sea, which denotes the natural man, as explained above (n. 511); the third part of the sea therefore signifies the whole natural man, and everything therein; and from the signification of blood, which denotes the falsity of evil, concerning which also above (n. 329:2). From these things the spiritual sense of this verse can be seen, namely, that the great mountain burning with fire cast into the sea, and the third part of the sea becoming blood, signifies that the love of self, when it enters and occupies the natural man, turns every scientific therein into the falsity of evil.

[2] The love of self is merely a corporeal love, springing up from the ebullition and fermentation of effete substances, and from the irritant action of these inwardly in the body, whence the perceptive [faculty] of the mind, which requires a pure atmosphere, not only grows dull and gross, but also perishes. That the love of self is from that origin, is evident from its correspondence with human excrement. For those who have been allured by this love, in the other life, love foul smelling filth above all other things, and the stench of it is grateful to them, which is a sign that the effluvium arising therefrom affects the sensory of their smell with delight, as it before affected the common sensory, which is extended on all sides by means of interior cuticles. From this fact alone it is evident, that the love of self is gross and sordidly corporeal above all loves, and, consequently, that it takes away all spiritual perception which pertains to the truth and good of heaven and the church; it also closes the spiritual mind, and fixes its abode entirely in the natural and sensual man, which communicates most intimately with the body, and not at all with heaven. It therefore comes to pass, that all those in whom the love of self rules are sensual, and see the things which pertain to heaven and the church, only in thick darkness; and when they are alone and think in themselves, they reject and deny them. The signification of the third part of the sea being turned into blood, because the great mountain burning with fire was cast into it, is now evident from these things.

Earth" is a general word that can be thought of as a container for other more specific words, as ground, field, or garden. Each of these means a person in an ascending series as that person learns truths from the Bible, thinks about them, and tries to apply them to life. The series represents the way of becoming good and wise. "Earth" and "ground" are terms that can go either way, as in the parable of the sower (Matthew 13:4-8) there was both good ground and bad ground, but "field" and "garden" mean minds that are regenerating towards good. "Earth" in the Bible can mean a person or a group of like-minded people as in a church. But it refers specifically to the external of the person's mind, or of the general thought of the group. If heaven and earth are mentioned together, then both the internals and externals of the mind are meant – something to note when reading the creation story.

In Revelation the word "earth" is used both as a ground level as we use it in its natural sense and also as the sense of a group. The action in this book takes place in the great middle zone of the spiritual world, where people first go and where they are sorted out. There are both evil people and good there, and sometimes at the end of a church the evil can have great influence before a great judgment comes. This level of the spiritual realm is called the "earth" to which the dragon was cast down (Revelation 12:9) and to which the stars fell (Revelation 12:4). The "earth" that swallowed the dragon’s flood means those still-sincere people within the church who discounted the flood of the dragon's falsities (Revelation 12:15).