http://en.wikipedia.org/wiki/Greek_Fire
This is pretty cool. An ancient and apparently overpowering weapon that, thousands of years later, we still haven’t recreated: “Greek Fire (also called Byzantine Fire and liquid fire) was a weapon used by the Byzantine Empire, said to have been invented by a Syrian Christian refugee named Kallinikos (Callinicus) of Heliopolis, probably about 673. Some people believe that he acquired this knowledge from the chemists of Alexandria. It was capable of discharging a stream of burning fluid, and was very effective both on sea and land, but it was used primarily at sea. It is rumored that the key to Greek Fire’s effectiveness was that it would continue burning under almost any conditions, even under water. Enemy ships were often afraid to come too near the Byzantine fleet because, once within range, the fire gave the Byzantines a strong advantage.”