Oh you can say it alright, it means black. It’s quite a common word too, and it’s given rise not only to toponyms and family names, but even designated origin products and some cultural references.
Like the Black forest (Schwarzwalder), Black forest ham and blackface (Gesichtsschwärzung).
Water stops fire because it spills over the burning mess and starves it of oxygen.
A burning lithium cell releases both oxidizer and fuel, which, because of the temperature, can now burn more of the lithium cell and release more oxidizer and fuel.
Which essentially burns down to LiPos can burn underwater and water won’t quench them.
Also, blasting a ship with water means that it will, eventually, sink. Spilling its own heavy fuel, and all the cargo onboard into the sea.