And he said to me,
This most likely is the same angel speaking in verses 1 and 7. Most often throughout the Revelation, angels are talking with John. The major exception, of course, is the original command to write the book of the Revelation (Revelation 1:10-19).
"The WATERS which you saw where the HARLOT sits, are
This expression seems a bit odd. When we sit on water (unless it is ice), we sink under. However, read how Jesus describes the last days in Luke 21:25-28 and His use of the sea and the waves. While the literal sea and waves may be "roaring" causing perplexity, if water is the container of spirit(s), then this verse here in Revelation indicates that the HARLOT will control or suppress any of the raging opposition to the beast (and the 10 kings). As a sidelight, look how much the 10 kings appreciate what the socioreligious organization (HARLOT) did for them (next verse).
Finally, the way this angel talks about "the WATERS", he may well be the angel of the WATERS (Revelation 16:4-7). The use of the past tense "SAW", indicates that the third angel has poured out his bowl already.
It is clear that this includes every being with a soul. Considering the major calamities the earth has gone through with the seal, trumpet, and bowl judgments, it is amazing that these people are not dispersed and off seeking their own revenge or salvation. However, these people are under the total control of the Babylonian HARLOT (socioreligious empire).
We should be aware that from these same WATERS, we, the redeemed, have come (Revelation 5:9). Praise the Lord that we are FROM these WATERS and not IN THEM (John 15:18-19-27)!