Navionics maps/creek beds

Hello! Starting to learn offshore fishing and saw several creek beds on my navionics maps. When I’m scanning over all these creek beds with my side and down imaging I’m not seeing any indent in the ground or depth change. Even on the map it does not show that the creek bed has any depth change to it or defined sides. I did see and catch fish on it, but my question is why don’t I see  a depth change or indent in the ground? I thought maybe silt filled it in over the years but wouldn’t I see a soft return on my 2d? My graph is a carbon 12, it is set up correctly, I have gone out and marked visible cover with it to verify. I also saw a roadbed on navionics web app but Scanned over it and didn’t see anything. Is it possible that the map is just outdated and the road got washed away?