Russell sought God, but never found him. The Psalmist really knew God, but felt cut off from him. Emphasis is not on water so much as panting. He never shows up. People want faith, answers to life's questions.
Philosophers say it is useless.
There are no answers, only chance occurances. B. Believers may feel this way, too. The psalm writer is honest with God about his feelings. Tears for food. Christians can get depressed.