Here are some excerpts from Swedenborg's "Arcana Coelestia" that help explain the inner meaning of this chapter:

AC 554. The subject here treated of is the state of the people before the flood.

AC 555. That with man, where the church was, cupidities, which are the "daughters"-began to reign. Also that they conjoined the doctrinal things of faith with their cupidities, and thus confirmed themselves in evils and falses, which is signified by "the sons of God taking to themselves wives of the daughters of man" (verses 1, 2).

AC 556. And whereas there were thus no remains of good and truth left, it is foretold that man should be differently formed, in order that he might have remains, which are "a hundred and twenty years" (verse 3).

AC 557. Those who immersed the doctrinal things of faith in their cupidities, and in consequence of this as well as of the love of self conceived dreadful persuasions of their own greatness in comparison with others, are signified by the "Nephilim" (verse 4).

AC 558. In consequence of this there no longer remained any will or perception of good and truth (verse 5).

AC 559. The mercy of the Lord is described by "repenting and grieving at heart" (verse 6). That they became such that their cupidities and persuasions must needs prove fatal to them (verse 7). Therefore in order that the human race might be saved, a new church should arise, which is "Noah" (verse 8).

AC 599. The subject here treated of is the state of the church called "Noah," before its regeneration.

AC 600. The man of that church is described, that he was such that he could be regenerated (verse 9); but that there arose thence three kinds of doctrine, which are "Shem, Ham, and Japheth" (verse 10).

AC 601. That the man who was left from the Most Ancient Church could not be regenerated, on account of his direful persuasions and foul cupidities (verses 11, 12); whereby he would utterly destroy himself (verse 13).

AC 602. But the man of the church called "Noah," who is described by the "ark," was not so (verse 14); and the remains with him are described by the measures (verse 15); the things of his understanding, by the "window," "door," and "mansions" (verse 16).

AC 603. That he would be preserved when the rest would perish by an inundation of evil and falsity (verse 17).

AC 604. And that the truths and goods which were with him would be saved (verse 18); and thus whatever was of the understanding and whatever was of the will, by regeneration (verses 19, 20); for receiving which he was to be prepared (verse 21); and that it was so done (verse 22).

557. People who immersed doctrinal matters concerning faith in their evil desires and who in consequence of this as well as of self-love conceived dreadful persuasions concerning their own superiority to others are the Nephilim, verse 4.