As the siege of Jerusalem dragged on, Jeremiah prophesied that whoever stayed in the city would die, but that those who left Jerusalem and allowed themselves to be captured by the Babylonians would live.  Some of the officials in Jerusalem did not like that message, and they put Jeremiah into the dungeon of Malchiah.  It was actually a cistern with a mud floor, and Jeremiah sank in the mud.  He was later pulled out.