It happened, when the people removed from their tents, to pass over the Jordan, the priests who bore the ark of the covenant being before the people;
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]