One Piece Chapter 1, page 25: Romance Dawn

That was the Gum-Gum Fruit!! The Fruit of the Devil, it's one of the secret treasures of the sea! If you eat it, your entire body becomes like rubber! And you will never be able to swim for the rest of your life!" Luffy's jaw drops in horror: "Whaaaaaaaaaat!? Aargh!!" Shanks yells: "You idiot!!!!" The scene then cuts to Luffy walking through the village, greeting the local fishmonger.