Many years ago, when I worked for Tommy Balfour in Orkney, we built an underwater-camera vehicle for the Fisheries Research people.
It was 'flown' just in front of a trawl net, and clearly showed a huge shoal of fishes swimming in front of the net and easily keeping pace with it for some miles, before eventually tiring and falling back into the net. The implication was that the fish could have swum away at any time but they chose to remain between the trawl-doors.
Geoff