"This is cold water."
Translation:He wai huʻihuʻi kēia.
This is a typical "class inclusion sentence" which tells which class of things a subject belongs to. The main part of the sentence often starts out with "He" a/an, and the subject is often at the end of the main phrase. This pattern does not contain a verb. Source: "Ka Lei Kaʻaheo: Beginning Hawaiian" by Alberta Pualani Hopkins.
Edit: aside from that, can someone explain why "anuanu" doesnʻt work for "cold" here?