Give it a few days to add a swim dish since they are outside- rather that the depth of water- make sure the depth of the container is shallow enough for the babies to get out of. Something an inch deep would be ok so that they dont get waterlogged and stuck in the container not able to get out. As they grow you can give them something deeper. Also having something very shallow is less likely to cause your momma hen too much stress when she sees her babies playing in the water.