That was my comment. It is taken directly from Revelation 21.
Then I saw a new heaven and a new earth; for the first heaven and the first earth had passed away, and the sea was no more. And I saw the holy city, new Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband; (Revelation 21:1-2)
The sea often represented doubt, uncertainty, strife, turmoil and fear. That is what is meant when Jesus calms the sea.
*And he said to them, “Why are you afraid, O men of little faith?” Then he rose and rebuked the winds and the sea; and there was a great calm. (Matthew 8:26) *
Jesus casts out doubt and fear and brings peace and calmness. Sometimes the sea represents the Gentile nations and the land represents Israel.
Then I saw another mighty angel coming down from heaven, wrapped in a cloud, with a rainbow over his head, and his face was like the sun, and his legs like pillars of fire. He had a little scroll open in his hand. And he set his right foot on the sea, and his left foot on the land, (Revelation 10:1-2)
To have your foot on a nation means that you control the nation. The angel controls both the Gentile nations (sea) and the nation of Israel (land).
The word sea appears several hundred times in the Bible. Sometimes the author is talking about a literal sea, just a large body of water, and there is no other meaning. Other times it has a spiritual sense such as Israel’s salvation in passing through the Red Sea but Pharaoh and his troops destruction in that same sea, or the flood of Noah as a prefiguring of baptism (1 Peter 3:20-21).
I don’t think St. John was really concerned with sailing and such when he wrote the Book of Revelation. I could be wrong however. He was a fisherman by trade. I really know nothing.