In order to get abs, first you need healthy ab muscles. This is crucial, but alone it will never get you to visible abs. Many people might have 6-pack abs under their skin and have no idea. The reason abs are so hard to get is because you need to have a low enough amount of body fat so the carved abs aren't getting filled over by fat.
So yes, diet > cardio > strength training. All are a necessary part. Truth is, it all depends how your body choses to burn that fat. Your body doesn't burn fat evenly at a constant rate. Certain parts of your body you'll notice thinning down faster than others. This is why it's a good idea to exercise everything, and to make that cardio a strong part of your exercise if you want your abs to stick out. You can't control it, so just try to make it work as best as possible.
If you want a pretty decent cardio workout that will help strengthen your abs at the same time, get a pair of diving/snorkling fins. Press both legs together, fins held close together, and swim like a dolphin by pushing your chest down, arching your back as you bring your chest back up, and following the motion down to your feet. It may feel awkward at first, but you'll get the hang of it.
They use that way of swimming for SCUBA diving a lot. It's used when the divers' legs get tired and lets them continue swimming from the abdomen and back muscles rather than relying on their legs to create the motion. However the motion you're doing will end up moving your feet up and down, so you'll still get most of your forward motion out of your feet, but your legs wont be the muscles to move them.
Find a video of a dolphin underwater and watch how they move, just try to mimic that with your full body as best you can.
I only say use fins because I don't know how much motion you'll get out of this otherwise.
