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It might appear those are boat wakes that start from the middle of river and cut across the flow to ‘heave to’ near the Tattershsll Castle. This pic may have been taken the same evening as LISAMI6. Does the pic capture the course of two vessels traveling upriver and stopping? Or does the pic maybe capture a time after the vessels have pulled in and are still idling with their cavitations being drawn into the flow of the river? 
Or not. But one would expect any outward surface signs of the the main flow of the river would follow course parallel to the river’s banks, and not divert to head into shore, right?