What does the the sand of the sea symbolize? (Revelation 13:1)

And I stood upon the sand of the sea, and saw a beast rise up out of the sea, having seven heads and ten horns, and upon his horns ten crowns, and upon his heads the name of blasphemy.

Revelation 13:1 - King James

⚪ The Time of Trouble

Rev. 13 [...]
13:1. And [I] HE stood upon the sand of the sea. — The sea represents the masses not under religious restraint. It is this symbolic sea that is to overturn and swallow up all kingdoms of earth in the great Time of Trouble. The proper understanding of the vision is located down at the edge of this sea, near the Time of Trouble.

Source : 🇺🇸 1917 - Studies in the Scriptures, Vol 7, The finished mystery, page 193 + Cover

⚫ A place of safety for one to stand

Revelation chapter 13
The thirteenth chapter of Revelation pictures John standing upon the sand of the sea and fitly represents the servant or anointed class standing in a place of security and gaining a view of Satan and his works. The sands mark the impassable bounds of the sea, and hence a place of safety for one to stand. "Fear ye not me1 saith the Lord: will ye not tremble at my presence, which have placed the sand for the bound of the sea, by a perpetual decree, that it cannot pass it; and though the waves thereof toss themselves, yet can they not prevail; though they roar, yet can they not pass over it ?" (Jer. 5:22) [...]
It is of much importance to determine what is symbolized or pictured by the sea. To say that it represents "restless mass of society" would hardly be adequate. The symbolic meaning of "sea", and which is abundantly supported by the scripture, is: The peoples of earth that are alienated from God and therefore ungodly, that mother, nourish, bear up and support the visible part of Satan's organization.

Source : 🇺🇸 1930 - Light, Vol 2, page 256, page 259 + Cover