When can i put my duckling in water

[dumb_cluck]

I've had mallards and recently got Welsh Harlequins and they both got to "swim" in a large pie pan at age 3 days. I do not leave it with them however, but each day they get a fresh pie pan of water to play in.

 

[Axle Quails]

How many inches of water ??? Should I put in

 

[Blob Chicken]

Mine always get 4 inches for the first few days ,then 6 inches ,then at about 10 days thay get a foort deep pool.