The waist coiled leash is the best solution.
- with the waist leash, the cord stays close to the surface and does not wander near the foil to get caught in it
- you are not moving the cord around with your feet movements in the water, so the coil cord does not tangle as it does with a knee of ankle leash
- running into / out of the water is easy, no walking on the leash. Really helpful in tricky situations where you already have the foil to manage, even more important with a also paddle
- of course, it does not drag in the water when flying
Only drawback is that you must be careful not to have the leash in your crotch when wiping out: have the leash attached to the side, not in the center of your back.