Should you ever wish to converse with a foreign duck:
Bengali - gack-gack
Danish - rap
Dutch - kwak kwak
Finnish - kvaak kvaak
French - coin coin
German - quack quack
Hebrew - ga ga ga
Italian - qua qua
Norwegian - kvakk-kvakk
Russian/Ukrainian - krya-krya
Swedish - kvack
http://oaks.ovg.org