User blog comment:Woohoot/Things that totally could happen, but won't cause... Manga.../@comment-10543621-20150524125222/@comment-5869646-20150524150351

Remember when Luffy was stuck underwater during the Arlong Park Arc? Nojiko and Genzo stretched his neck to get his head above the surface so he could breathe.

Seastone and water prevent a DF eater from using/controlling their powers. But Luffy's body has been essentially permanently altered, so he can still be stretched by outside sources no matter what. Except... when BB uses Kurouzu on him. That seems to completely remove his rubber properties, because the darkness sucks in the very Devil Fruit power.