[Dan 12:6-7 NASB] (6) And one said to the man dressed in linen, who was above the waters of the river, "How long [will it be] until the end of [these] wonders?" (7) I heard the man dressed in linen, who was above the waters of the river, as he raised his right hand and his left toward heaven, and swore by Him who lives forever that it would be for a time, times, and half [a] [time;] and as soon as they finish shattering the power of the holy people, all these [events] will be completed.
The phrase "above the waters" seems to be associated with the waters above, as in, above the "firmament" that supports the waters above:
[Gen 1:6-10 NIV] (6) And God said, "Let there be a vault between the waters to separate water from water." (7) So God made the vault and separated the water under the vault from the water above it. And it was so. (8) God called the vault "sky." And there was evening, and there was morning--the second day. (9) And God said, "Let the water under the sky be gathered to one place, and let dry ground appear." And it was so. (10) God called the dry ground "land," and the gathered waters he called "seas." And God saw that it was good.
[Psa 148:4 NIV] (4) Praise him, you highest heavens and you waters above the skies.
[Rev 10:1-2, 5-9 NLT] (1) Then I saw another mighty angel coming down from heaven, surrounded by a cloud, with a rainbow over his head. His face shone like the sun, and his feet were like pillars of fire. (2) And in his hand was a small scroll that had been opened. He stood with his right foot on the sea and his left foot on the land. ... (5) Then the angel I saw standing on the sea and on the land raised his right hand toward heaven. (6) He swore an oath in the name of the one who lives forever and ever, who created the heavens and everything in them, the earth and everything in it, and the sea and everything in it. He said, "There will be no more delay. (7) When the seventh angel blows his trumpet, God's mysterious plan will be fulfilled. It will happen just as he announced it to his servants the prophets." (8) Then the voice from heaven spoke to me again: "Go and take the open scroll from the hand of the angel who is standing on the sea and on the land." (9) So I went to the angel and told him to give me the small scroll. "Yes, take it and eat it," he said. "It will be sweet as honey in your mouth, but it will turn sour in your stomach!"
But what of the man above the waters of the river? Is that significant?