Here’s a look at a Vessel Assist ‘rescue’ from Seattle, with some details from local rigger Chris Tutmark. Plenty of chat about it here.
Note that the masthead was lodged into one of the small trussed boxes along the bridge edge. One of these can be seen in the black and white pic in the link below as one of the vertical members of the bridge. If they had gotten the boat free quickly when things first got stuck, the mast “may” have survived. As it was, the only question was how many pieces it was going to be in once the boat was freed. And it was a keel stepped mast, so dropping shrouds would have only changed where it broke, not whether it broke.
For this spot, the surface water almost always runs to the west (going left) as it is fresh water coming from the Locks and the spillway. For those who do not live near the bridge, here is some history.