Duck typing and (java) interface concept

I just read the Wikipedia article about duck typing, and I feel like I miss an important point about the interface concept I used to in Java:

"When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck."


class Duck:
    def quack(self):
        print("Quaaaaaack!")
    def feathers(self):
        print("The duck has white and gray feathers.")
    def swim(self):
        print("Swim seamlessly in the water")

class Person:
    def quack(self):
        print("The person imitates a duck.")
    def feathers(self):
        print("The person takes a feather from the ground and shows it.")
    def name(self):
        print("John Smith")

def in_the_forest(duck):
    duck.quack()
    duck.feathers()

def game():
    donald = Duck()
    john = Person()
    in_the_forest(donald)
    in_the_forest(john)

game()

what if, in in_the_forest, I write:

• does it quack like a duck ? yes
• does it have a duck feathers ? yes
• great, it's a duck we've got !

and later, because I know it's a duck, I want it to swim? john will sink!

I don't want my application to crash (randomly) in the middle of its process just because John faked to be a duck, but I guess it wouldn't be a wise idea to check every single attributes of the object when I receive it ... ?