This is the Argentinian Blue-bill duck, a cute but unremarkable looking duck but below the water it holds an incredible secret – it has a massive penis!
The duck has an average penis length of 8 inches (20cm) – that is longer than a human whose average penis size is 6 inches.
And the longest recorded penis of the duck is a remarkable 42.5 cm (17 inches) long. (photo below)
Relative to size this is the longest penis in vertebrates (animals related with us).
Biologists believe that the remarkable size of this penis may have evolved in response to competitive pressure in these highly promiscuous species, removing sperm from previous matings in the manner of a bottlebrush.