Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word:
Be sure you always carry water when visiting the me zoo (みず). That's a zoo with rows and rows of cages of... me. And I'm thirsty!
Can I have some water or tea?
Don't forget to bring water when you climb Mt. Fuji.
Give me a cup of water and some love, please.