lithium will oxidize (burn) with water but heat will still be dissipated by water and weight of pack will mean it will sink. Sand is just starving the lithium of oxygen - it won't actually put out the fire..

cesium will explode on contact with water...

I heard pure sodium is bad too...

Burns hot and fizzles / skims around the surface of water as it burns - needd to be stored in oil or will self combust on contact with air...

We used to borrow it from the lab and throw it in the school pond... ducks weren't so happy...

Lithium from batteries is normally stable in a matrix but if over charged the lithium can collect at the anode and hence combust.

Hmmm, yes... :lol: I have to keep my CsPo batteries in a vacuum chamber because any humidity in the air will ignite them through their casing. :surprised: :rofl: