What is a major danger of using water to extinguish lithium battery fires?

Using water to extinguish lithium battery fires is particularly dangerous because lithium reacts violently with water, producing hydrogen gas and heat. When lithium is exposed to water, it ignites this hydrogen gas, causing the fire to escalate and become even more difficult to control. This reaction generates additional flames that can spread the fire, endangering both the surrounding area and individuals who are trying to extinguish it.

The other options do not accurately capture the primary hazard associated with lithium battery fires. For example, the claim that lithium batteries are waterproof misses the key issue of their reactivity with water. While it may be true that some components of a lithium battery have certain resistances, it does not negate the fact that using water is highly inadvisable. Additionally, it is incorrect to say that water enhances the burn rate of lithium in a direct manner; rather, it initiates a dangerous reaction. Lastly, cooling a battery too quickly can indeed lead to thermal shock, but in the context of lithium fires, the immediate danger stems from water's reactivity with the lithium itself.