I've just recently received my Amiigo and was surprised when trying to start a swim workout that the foot pod was necessary. I know that they've (or somebody has) mentioned that in future they may release an ankle strap and SW for kicking analysis, but my current understanding is that the foot pod is not used at all for swimming.
It seems odd that you'd need the foot pod to start an activity where it is not used at all. I image the same complaint exists for people only doing upper body exercises, where you're not using your lower body at all.