Cave bends light. Inside a Mexican cenote earlier week. Swam into a chamber that has a small hole in the roof that let's in a beam of light when the sun is overhead. It was 3pm and the light beam came in at an angle and bent backwards close to the bottom of the cave as my underwater picture shows. Why? I think the light passes from an upper layer of fresh water and then twists as it enters a denser layer of salt water. I stand to be corrected.