I'm a BIG fan of DL but even I'd say no. DL works best when the soil can stay lightly moist (not soggy) & turned/scratched frequently. Ducklings won't scratch like chickens & certainly won't keep the DL dry enough - though you could rig some type of pebble/mesh divider so that the water falls down before it reaches the DL. I'd still say it's a huge hassle.Can I use the deep litter method in a brooder with ducklings?
If you do DL with adult ducks I'd make sure there were scratch-type birds in the mix (ie, chickens) & that there was a floor divider (like an overflow catcher) between where they swim & the DL.