I would even carry them to a swimming place if they can't walk there on their own! There's noting better for duck-legs than exercise in water without all the weight pushing down on their feet. My drake Limpy spends entire days in the pool, it seems to help him.I'm ahead of you on that, hopefully they start feeling better soon. When do you think it would be fine to let them out? I have tons of places for them to swim so hopefully they get strength to do so.
