This achievement can easily be done on the mission taming Gollum during the boss fight you will need to fish at a peir to get a fish to fling at Gollum once this is done a highlighted area will appear do not use it and Gollum will go back to the wall allowing you to fish again.
When fishing to do it perfect only press the button when the circle around the button disappears and a small flash will appear behind the button you will know it is done
correctly by a large amount of studs appearing around your character.