In the “static apnea” discipline in freediving, many cool pictures of athletes are taken underwater in a way that plays with the reflection of the athlete in the still water surface. This can lead to pretty spooky pictures (like the one of Victor in the top left). We do have other experiences with water, where there are areas where we can look in (or out), but then others where we can’t: In the bottom left, you see Mats and his shadow, even the individual tiles very clearly in the water. But the further back you look, the more you notice that the picture was taken from outside the water, because you start seeing more reflections in the water surface. In the bottom right, taken from within the water, you see reflections of all the divers and the lane markings in the surface except right at Edvin’s elbow, where we look out of the water and see what’s happening above the pool. And then in the top right, we don’t see the water surface at all — the only reason we know we are looking at Alex from within the water is that there are bubble rings floating between us and him. So what is going on here?

Continue reading →