In the few years I was with that movement I never encountered an Arian or other non-Trinitarian.
But that being said, the way they often explain it is a bit of a Modalism approach, in that using the states of water aka liquid, solid, and gas was a typical way of explaining the Trinity. But what can you expect when so many of them eschew formal theological schooling, and don't see the importance of studying the ancient creeds, church fathers, etc.
Here is the formal statement of Rhema Bible Training Center (the place where WOF officially started)
What We Believe
THE GODHEAD—Our God is One, but manifested in three Persons—the Father, the Son, and the Holy Spirit, being coequal (Deut. 6:4; Phil. 2:6). God the Father is greater than all; the Sender of the Word (Logos) and the Begetter (John 14:28; John 16:28; John 1:14). The Son is the Word flesh-covered, the One Begotten, and has existed with the Father from the beginning (John 1:1; John 1:18; John 1:14). The Holy Spirit proceeds forth from both the Father and the Son and is eternal (John 14:16; John 15:26).