See? A better opinion from more of an expert!So the duckling looks like it has a curled foot. You can tape the foot with making tape or painters tape to hold it in place. I believe it can be fixed a few days. There was a thread on here recently where they talked about. I can't find it.
Here is an older one.
https://www.backyardchickens.com/threads/day-old-ducklings-feet-are-curled-under.50180/
Swimming can help them strengthen their legs while not being strained. If it has having a hard time walking this would be beneficial. You will get the most benefit from it if they can touch the bottom and must float. Either way they love swimming and it can't hurt. Just make sure the water is warm.