Water drop cut diamonds occur due to a phenomenon known as total internal reflection. When light enters a diamond, it slows down and bends or refracts. The diamond's pavilion angles are designed to reflect the light back through the diamond's crown. However, if the diamond is cut to the correct proportions, the light will undergo total internal reflection, bouncing back and forth inside the diamond until it exits through the pavilion. The result is a diamond that looks like it is glowing from within, with a beautiful and bright sparkle. This effect can be enhanced by the way the diamond is cut into a water droplet shape, which perfectly captures and reflects the light from all angles, giving the diamond a unique and stunning appearance.