Thank you for rescuing the little fellow. The good news is that it sounds you are taking great care of him, i.e., letting him swim in the daytime and bringing him in at night. If you did not bring him in, he would freeze because of the lack of feathers. From the description, he may be less than a month old, so the bad news is that until he gets feathers he is going to need care for about the next 3-4 months.

Your best bet would be to turn him over to a wildlife rehabilitator who will be able to properly care for him for the next few months. Until he is approximately 6 months of age, he will be too small to protect himself from predators and if he is a mute swan, he will need to be pinioned (permanently prevented from flying per state laws). If he is a Trumpeter or Tundra swan, which no one is going to know until he starts to turn color around 6 months of age, he may be a protected species and cannot be in your possession.

You should feed him a mixture of cracked corn and poultry layer pellets submerged in water. He must have the food in water to eat. Provide him with fresh lettuce, swans seem to like romaine over iceberg because of the leafy vegetation. You can also provide him with a little bread not much. We hope this information is of benefit. Please let us know how this situation progresses. The Regal Swan