When I saw this image, I discounted it as the creature pretty quickly, mainly because I was there the same morning on the 27th August at the Foyers campsite on the other side of the river. I quote from my trip
report published four days before this photograph.
When I arose on the Sunday morning at Foyers, I looked out to the area where the River Foyers met the loch. The heightened flow of the river was rushing down to meet the loch and there was a lot of disturbance where the two collided. The general flow of the vaster body of the loch water was from the south west up the loch. However, the river water was hitting it at almost a right angle.
The result was a wall of resistance as the river water tried to merge with the main waters. The dynamics of this interaction led to the river water rotating in the direction of the loch water but also turning back towards the river giving us a sort of whirlpool.