It almost happened to me at a zoo in Thailand. The hippo was clearly trying to fling poop on me, intentionally. I have it on video.
I was crossing the area on a narrow suspended bridge. The hippo in the water saw me and went straight to the closest bank. I'm not sure how I knew what the hippo was about to do, but I somehow KNEW. I started saying "don't you do it, don't do it" even before the tail started flapping. Then the tail started and then poop started flying everywhere.
I guess it's one way they claim the territory.