It's always going to have the same ratio between the diameter across the top and the height, because these are lines right over here. So at any given point, the ratio between this and this is going to be the same. So at any given point, the diameter across the surface of the water, if the depth is h, the diameter across the surface of the water is also going to be h. And so from that, we can figure out what the radius is going to be. The radius is going to be h over 2. And so the area of the water surface is going to be pi r squared, pi times the radius squared, h over 2 squared. That's the area of the surface of the water. And of course, we still have the 1 third out here, and we're still multiplying by this h over here.