It is as thick as your arm, gloopy and smells disgusting - and it has just been caught on camera for what is believed to be the first time.
A crew has managed to film a whale shark - the world's biggest fish - expelling food waste, which was then scooped up for research.
The footage forms part of a BBC Natural World wildlife programme: Whale Shark.
Whale Shark is on BBC Two on Tuesday 18 November at 2000 GMT.
Bookmark with:
What are these?
E-mail this to a friend