When swimming underwater, why is vision blurred when you open your eyes, but clear when wearing swimming goggles?

sequoianoir

The curvature of the eye ball (specifically the lens at the front) is what focuses the light on to the retina at the back. When water comes into contact with the lens it changes its optical parameters. Swimming goggles stop this happening by keeping the water away from the eyes and usually, to stop any optical distortion of objects viewed, have perfectly flat surfaces through which you look. Feb 07 04, 6:51 PM