Think about sinking to the bottom of the Marianas Trench and then inflating a balloon just enough to make you neutrally buoyant. The net force on you will be ze

Think about sinking to the bottom of the Marianas Trench and then inflating a balloon just enough to make you neutrally buoyant. The net force on you will be zero, but you'd still be crushed by the pressure, which is the effect of many kilometers of seawater above you. Another way to think of this is to imagine a small sphere (like the size of a basketball) around the very center of the Earth. The matter in that sphere feels no net gravitational force, but it has to push back against the entire mass of the rest of the Earth, which is trying to fall into it.