I have mine swimming from day 3 on. First it is a paint tray with warm water placed into the bath tub. Have a washcloth hang over the side so they can get out. They will splash so here you have an area you can easily clean after wards. You must be present at all time, because they can drown if they get exhausted. You will see when they have enough, because they just start to stand around doing nothing. That is when you take them out, paper towel dry each one of them and put them back into the brooder underneath the warm lamp. You will also notice that they start to preen within days. Not that they are producing the preen oil yet, but they do perform the grooming motions. Early water exposure does promote the preen gland and they will produce their oil earlier then without swimming. Never provide a water swimming pan in the brooder. They just don't know when to stop, get chilled and can die. Controlled environment and warm water only.