To be fair, I have just found a FAA document which recommends fire fighting methods for lithium type batteries in portable electronic devices, which states:
"Utilise a Halon, Halon replacement or water extinguisher to extinguish the fire and prevent its spread to additional flammable materials.
After extinguishing the fire, douse the device with water or other non-alcoholic liquids to cool the device and prevent additional battery cells from reaching thermal runaway.
Do not use ice to cool the device."
Still, I don't know if I'd want to use water for a battery in a compartment with other electrical equipment and wiring.