wood = duck = witch

Brought back memories of the Monty Python film "The Holy Grail"

Sir Bedevere: Does wood sink in water?

--No, no, it floats!... It floats! Throw her into the pond!

Sir Bedevere: No, no. What else floats in water?

--Bread.

--Apples.

--Very small rocks.

--Cider.

--Gravy.

--Cherries.

--Mud.

--Churches.

--Lead! Lead!

--A Duck.

Sir Bedevere: ...Exactly. So, logically...

--If she weighed the same as a duck... she's made of wood.

Sir Bedevere: And therefore...

...A witch!

Done