Use the verb douse to describe covering something with water or other liquid. When you're camping, you douse the campfire with water when you're done with it.
Douse often involves water, but you could also douse your French fries in ketchup. Douse can describe the act of extinguishing a candle, or even turning off a light. You might douse your bedroom light when it's time to sleep or simply douse a candle by blowing it out. To pronounce douse correctly, remember that it rhymes with mouse.
If you need a word that makes cave sound more interesting you might try grotto, an Italian loaner that is used in English to designate small caves or artificially constructed ones. Italian developed the word from its parent Latin, where the word was crypt: a word that has also made its way into English with a different but related meaning.