I think BJ's analysis is likely correct, the boat is stuck in the side channel, not where the bridge opens. It is hard to imagine getting a boat in that spot on purpose, and the current there is stronger than the center. On my last trip out of the locks a large ketch got sidways at the end of the lock and spun down the channel towards the same bridge. The skipper finaly got it all sorted, but the current when the lock opens, especilaly durring an ebb can be pretty fast.
Now why they did not pull the boat over on it's side to get it out is another question.