Ok, I'm almost certainly incorrect but I want to see where I'm going wrong. Let's say the earth had only ocean, and a little jut of land somewhere amongst this ocean that had a turbine that collected energy as water ran through it. Now consider the moon orbiting the earth, pulling the water up at the closest point between the earth and moon, which then disperses again as the moon continues orbiting. Wouldn't this cause water to run through the turbine. And if the earth+moon was a closed system and the moon was on a perfect trajectory so that it never fell to the earth, wouldn't this be infinite energy over infinite time? What am I getting wrong? Thanks.