When you say daily swim, I'm assuming you mean in water 1/2 deep....
Just remember they aren't waterproof since the only place ducklings get waterproofness from is mama's feathers. My dad had to teach me this as a child, by rescuing the ducklings off the pond where I'd put them, before they got waterlogged and sunk!
I love all my small feathered friends, but ducklings and goslings are somehow the sweetest and funniest, so more than make up for their smelly messiness