I don't get it. I don't get why guys are so skeptical about Caribou's devil fruit in particular. Is he that special? When have we ever needed more evidence than the demonstration of the devil fruit itself, and other character's own judgment, for us to acknowledge a persons's devil fruit? Is the idea that he has a logia so inconcievable that we must belittle ourselves to being dependant on said person explicitly telling us that he is so, for it to be accepted? Is it because an attack was shown to not pass through him? If so, that is just a common misconception which I admittedly accepted for a long time. But then one day I just thought to myself 'Wtf, logias ain't intangible at all'. Logia users simply react to attacks the same way their elements would in reality. Kizaru's light is intangible by nature, so attacking him would also have that effect. Smoker's smoke is also intangible by nature so attacking him would also have that effect. However, when Ao Kiji is attacked, he shatters like ice would do in reality when hit. With that said, when Caribou was attacked, his body simply reacted to the canon ball the same way a swamp would in reality; it just sank in.