Ok, we are not in the same category as you, as we have 3 boys, but wanted to give a perspective on depth. We made ours 9 feet (wanted 10) with a diving board. The kids only venture to the shallow end when they want to get away from the person chasing them, otherwise they spend nearly 100% in the deep end. I've never even come close to hitting the bottom with a cannon ball, and even have a hard time hitting the bottom doing a feet first pencil dive. We spoke to many people before building ours, and nearly everybody with kids always wished they made the pool bigger and deeper. We also have benches on both sides of the deep end, so the kids can hang out without treading water.