Yup, Swimming is a crazy good cardio workout but you will be supprised at how much you will move your foot doing it.
The same applies to cycling...
Possibly look into Rowing. Good work out and it may not move your foot as much but will require you to push with it...without knowing exactly whats wrong with your foot I don't know how that will fair for you.
You may also just want to keep off the foot until it heals properly and then go full bore.