Luke 21:11
And there will be great earthquakes in various places, and famines and
pestilences; and there will be fearful sights and great signs from heaven.
The meaning of PESTILENCE is a contagious or infectious epidemic disease that is virulent and devastating
About the last days, right before Christ returns. the sea and waves roaring is actually not ocean sea water here, refer to Rev 17:15
v25 is understood as referring to the nations and their rulers and their perplexity, related to men's hearts, not literal ocean water is Christ speaking of.
Luke 21
25 “And there will be signs in the sun, in the moon, and in the stars; and on the earth
distress of nations, with perplexity, the sea and the waves roaring; 26 men’s hearts failing them from fear and the expectation of those things which are coming on the earth, for the powers of the heavens will be shaken. 27 Then they will see the Son of Man coming in a cloud with power and great glory. 28 Now when these things begin to happen, look up and lift up your heads, because your redemption draws near.”
Revelation 17
12 “
The ten horns which you saw are ten kings who have received no kingdom as yet, but they receive authority for one hour as kings with the beast. 13 These are of one mind, and they will give their power and authority to the beast. 14 These will make war with the Lamb, and the Lamb will overcome them, for He is Lord of lords and King of kings; and those
who are with Him
are called, chosen, and faithful.”
15
Then he said to me, “The waters which you saw, where the harlot sits, are peoples, multitudes, nations, and tongues. 16 And the ten horns which you saw on the beast, these will hate the harlot, make her desolate and naked, eat her flesh and burn her with fire. 17 For God has put it into their hearts to fulfill His purpose, to be of one mind, and to give their kingdom to the beast, until the words of God are fulfilled. 18 And the woman whom you saw is that great city which reigns over the kings of the earth.”
Same idea in Rev 21 where it says no more sea.
Now I saw a new heaven and a new earth, for the first heaven and the first earth had passed away. Also there was no more sea. 2 Then I, John, saw the holy city, New Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband.
Other verses about sea in Revelation are the actual ocean waters in some of the verses. Perhaps not all though.