A DI EVEN THRO IT IS POINTED DOWN STILL SENDS SINGAL TO THE SIDE AND IF THE OBJECT IS HARD ENOUGH FOR SINGAL TO RETURN BACK ,IT WILL PICK IT UP AND GIVE DISTANT AS IF IT LOOK LIKE IT WAS UNDER DUCER WHEN IT IS COMPLETELY SIDE WAYS, 2D WILL DO THE SAME THING.YOU SEE THIS OFTEN AROUND BRIDGE PILLING AND BOAT DOCKS