Unless you can completely fence in the entire pool area (top to bottom), the only safe place will be the barn. However, this is going to pose several problems during nesting time. One, you will have to prevent pests such as rats and ants from entering the barn and getting into the nest due to the swans' food inside the structure. The food will need to be in or near a water bowl to ensure that the swans have water to feed and not choke. The bowl or pan will need to be a zero entrance for the young cygnets to get used to eating, bathing an preening. (You can also use a paint rolling pan lined with a towel to prevent slipping). The need for a water feature is going to be the second problem because you will need a water feature that the young cygnets can enter and exit without hurting their legs and the parents are able to watch and interact with them.

You can provide "pool time" in something like a rubbermaid bin, but this means that the parents are going to freak out everytime that you take the cygnets for a swim. The parents are not going to tolerate you picking up their cygnets and allowing them to swim with the parents nearby. This will cause the possibility of an injury to the young birds as they are called by the parents and try to exit the bin. The cygnets are also going to stress by not being near their parents. So, the scenario you are posing is going to be interesting.

I am going to ask Bob Knox from Knox Swans to also contact you with suggestions for the nesting swans to help with the issue of an indoor water feature. He has indoor pens and will be able to offer some viable suggestions for you. The Regal Swan