Low bodyfat is not enough to get abs, i mean your body fat MUST MUST be low in order to see them but if you're already below 12%, doing ab exercises are a must, if you're not below 12% forget it and focus on cardio and diet, if you're below that keep reading..
hanging leg raise 4 sets 10-12
deline sit up 4 sets 10-15
russian twist 4 sets as many as possible
leg lifts 4 sets 12-15
crunch 4 sets as many as possible
Add weight if its too easy..