What property of water causes you to experience pain when you do a belly flop?

The pain experienced during a belly flop is primarily due to water's high surface tension and its incompressibility. When you hit the water flat on your stomach, the surface tension resists the force of your body, creating a sudden impact that can cause pain. Additionally, because water does not compress, the force of the impact is transmitted through the water, leading to a hard landing despite its liquid state.