This is what Metzer Farms says about swimming:Anyhow I’m in southern Louisana and it’s hot and sunny so I’m not worried about them catching any chills but are they ready to swim?
"Ducklings and goslings can be introduced to swimming water as early as one week of age but you must be very careful. They must be able to walk in and out of the water very easily. The water should not be too cold and they must be able to find their heat lamp for rewarming without difficulty. As they have no oil on their feathers at this age, they cannot be in the water for long periods or they will become waterlogged and chilled. Do not allow this to happen! But this exposure to water speeds the development of their oil gland and they can probably be swimming freely by five or six weeks of age."
Source: http://www.metzerfarms.com/RearingInstructions.cfm
I only say about warmer water because someone here seid their duckling would take a drink of cool water then convulse and die instantly
Like the cool shocked their bodys
That's sort of how it happens, though it usually happens when they drink a lot of cool or cold water all at once. This can be avoided by refilling empty waterers with warm water.