The idea that a short trip over a bridge could bore a person... I don't know what that means about the author or culture. 40 minutes on a bridge wouldn't be a bore.
The bridge itself; the flow, depth, and content of the water; the shades of color of the sky, the clouds shape, color, height, and movement; the critters flying or swimming; the events of the day before or next.
Could keep naming things to experience or think about, don't need that constant feed of input unless you are running away from thinking about something.