Snell's Window on the Olympics

Olympic Swimmers

I did a bit on Snell’s Window last summer, and you can see that effect quite clearly in photos 1 and 8. If you look carefully at photo #6, you can see the edge of the window at the top of the shot. Below that there is the total internal reflection, which is quite obvious with the first two swimmers. Now imagine you’re a predatory fish, and your target is swimming away from you and approaches the surface — he would see another fish come into view — the reflection, and if the fish then breached the water it would disappear completely, except for any glimpses possible from the disruption of the surface.