Firefighters often submerge the vehicle for weeks or else it would reignite…

I would like to see a source on that. Because I’ve talked to firefighters who said EVs can be put out like any normal car, you just need much more water.
Which is a problem, because it means you need to call a bigger fire truck or maybe even multiple for an EV fire, but I’ve never heard of an EV needing to be submerged for weeks (how would that even work?).