Yes, but if the swimming water is in the brooder you are going to have to do a full clean of the brooder much more often, they need to be able to be warm and dry and that swimming water will end up everywhere but in its container.
I think it would be better to have the swimming time limited and outside of the brooder, or maybe right before you plan on cleaning it anyway.
They can start swimming by day one, but again, limited and given time to be warm and dry