CatBus, the problem with your imaginary duck hypothetical is that it relates to nothing. If theists viewed God in that way it would be just as nonsensical.
Most theists believe in God based on what they can perceive and find it implausible that a deity doesn’t exist based on those perceptions. There are very flawed conceptions of God and I agree with Frink, at least to an extent, that really understanding God is beyond our capacity. But that doesn’t mean we can’t have a basic (and necessarily flawed) understanding that does us some good.