and when those who bore the ark were come to the Jordan, and the feet of the priests who bore the ark were dipped in the brink of the water (for the Jordan overflows all its banks all the time of harvest),
There is additional information here in  Joshua 3:17.  At some point in the progress of Israel over Jordan, the priests moved into the very midst of Jordan, where they stood until the passage was completed.  "The priests bearing the ark first took up their stand on the brink of the river, but as they advanced to mid-channel, the river was dried up before them."[26]