Just because I have yet to see any one make an entry into the challenge Q set before us a number of months ago....
I present to you, in the factoid category: The Dolphin
How do you know if a dolphin wants to have sex?
Males are probably the easiest to detect. They will swim around, sporting an erection (anywhere from 10 to 14 inches long for a Bottle-nose), and will have no bones about swimming up to you and placing their member within reach of your hand. If you are in the water, they may rub it along any part of your body, or wrap it around your wrist or ankle. (Dolphin males have a prehensile penis. They can wrap it around objects, and carry them as such.) Their belly will also be pinkish in color, which also denotes sexual excitement.
And in the freestyle category:
There once was a goddess named Venus, Who sought sex outside of her genus. And none could come close To what she sought most; A man with a prehensile penis.