They'll know how to swim.

It's your job to offer a diet similar to what they'll be eating in the wild, supplementing with store-bought. Chances are when they get older they'll couple up with a wild one and learn from them.

Imprinting may be a problem, I'd minimize contact with them as much as possible, and when they have feathers start to really let them out, free-range, instinctual feeding habits will kick in quickly. They'll probably return home for a while until they find a mate, a nice pond, or not. Make them a safe pen when they are older, maybe something like a chicken tractor you can move around while they eat grass or bugs?

They'll need some type of heat source until they get some feathers (where are you located? is it still cold?). Protection from predators (a weasel can get in a 1x2" opening), water & of course what natural food you can scrounge up, and shade.

If they survive in captivity when young I think they'll cope & adjust well. Sometime wild animals just don't do well in captivity, so be forewarned.
That's all I can think of for now.
Brendasue