I don't think flooding any metal fire with water is a good idea as normally the metal rips the oxygen out of the water leaving hydrogen, sand is a better choice. Just throw sodium in to water and see what happens. Even in a central heating system the gas that has to be vented from radiators is hydrogen ripped from the water by the iron in the rad. The better lithium battery to day and should have been used in the 787 is Lifepo4, it does not catch fire like lithium ion, check out the number of fires after crashes of Tesla cars Li ion against GM Volt Lifepo4 that have never caught fire.