The medieval moat is often depicted as a beautiful water feature filled with jaw-snapping alligators surrounding towering stone walls, with a drawbridge that opened and closed on cue. This is not necessarily an accurate representation of medieval moats. Moats were mostly utilitarian in nature and the castle's inhabitants depended on it for their lives.
The primary purpose of the medieval moat was to protect the castle it surrounded. Surprisingly, not all moats contained water. When a water source was not available, trenches were dug and filled with wooden spikes. These spikes posed danger to horses and men attempting to capture the castle. A water-filled moat, however, was a much better deterrent to anyone who might consider tunnelling under to penetrate the castle walls. Moats also provided an inhospitable surface for siege ladders and towers, making theses ineffective tactics against moat-protected castles.
Ideally, the castle was built near a stream, river or lake that would be dammed and diverted to fill a man-made moat. This job was performed by castle servants or slaves, often prior to the construction of the castle itself.
Privies were constructed near the exterior walls of the castle with sloped chutes to transport waste effectively out of the castle. The waste poured into the moat surrounding the castle, creating a cesspool of human waste. Prior to this more modern type of plumbing, chamber pots were used and simply emptied into the moat below. In some instances, human waste, rotting animal corpses and refuse in general were intentionally dumped into the moat to make it more of a deterrent to potential intruders.
While many movies depict moats filled with snapping alligators or crocodiles, this was not often the case. The climate in most places did not support these animals. They require warm, almost tropical, conditions. Europe is cool with cold winters. Even if the animals were imported, they would not survive because of the fact that they are cold-blooded and would remain in an almost catatonic state because of the cold temperature.