I've been letting my ducklings swim/walk in a water filled tote. It's deep enough that they can swim if they want but not so deep that they can't walk in it. How do you know when it's time for them to come out? They can't get in and out on their own so I just sit with them but I never know when to take them out. They are still all downy amd I imagine are only maybe 2 weeks old?