The device was returned, but that pattern is the ship that likely carried/deployed the device, not the device itself. Per another post that box is part of a fi

The device was returned, but that pattern is the ship that likely carried/deployed the device, not the device itself. Per another post that box is part of a fine grained positioning system, so I'd expect the ship deployed it then started doing whatever it was doing, and the fisherman trawled it up in the meantime.