Marguerite

Marguerite (also translated as Margaret) is a character from One Piece.

Chapter 514
Marguerite goes Skinny Dipping in a lake wearing only a Loincloth as she bathes an unconscious Monkey D. Luffy along with Sweatpea who was clothed. After she washes Luffy's chest, she then grabs onto Luffy's private part trying to pull it off thinking it was a left over mushroom that was growing on his body from the mushrooms that they were removing from him but then realize that Luffy is a man from Grandma Nyon pointing it out.

Trivia

 * Marguerite was clothed in the anime adaption's version of her skinny dipping scene in episode 408.