Radar doesn't pick up some of the trash out there that can really ruin your day! Have seen logs, trunks, house roofs, etc. that can make nightmares.
Actually, the new 3G and 4G radar systems WILL pick up the trash. You can see crab pots, gulls floating on the surface and flying off as your boat approaches, pretty much anything out there including styrofoam cups. The only 3G Radar system I've seen personally is the Lowrance, and it was absolutely incredible. So in this situation, radar is definitely your friend.