Concur. The color of the "surrounding objects" are very grey, like froth. There does seem to be a single small boat to the southeast of it (between it and the other freighter), but the pattern of the surrounding imagery is too irregular to be boats. Why would boats of differing size and shape but identical color surround a boat?
There are an awful lot of boats in this river... but then again, it's one of the most major rivers of Earth's history.
I'm sorry, I'm still not convinced. The objects appear to have square edges and are very un-wakelike. Check out the boat three boats away to the north and you will find similar objects, but only on the starboard side of the ship. Very uncharacteristic of a wake.
No Longer There 
There are an awful lot of boats in this river... but then again, it's one of the most major rivers of Earth's history.