The path of a diver jumping from a platform is modeled by a quadratic function $h(x)$, representing the height of the diver in meters above the water surface, $x$ meters horizontally from the edge of the platform. The diver reaches a maximum height of $5$ meters above the water when $x=2$ meters horizontally from the edge. The diver enters the water at $x=6$ meters horizontally from the edge. Based on this model, what was the initial height of the platform above the water, in meters (i.e., the height when $x=0$)?