h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

There's an article in the August Scientific American that states something that seems to me to support to Aquatic Ape theory.

It says that a group of people called the Mokan who live in southeast Asia have the ability to make their pupils smaller while underwater. This allows them to use their eyes as pinhole cameras, allowing them to see underwater twice as well as most people. THe author also suggests that this can be learned b focusing on objects while swimming underwater as a child. If this is true, it suggests that humans must have done a lot of swimming as some recent stage in their evolution; why else would their eyes be able to do this?

I haven't seen the article you refer to, but I don't understand how shrinking the pupils increase vision in an underwater environment, where I am assuming you have lower light levels (or are you referring to polarisation? even so I would assume a large pupil would allow more light onto the retina).

Even taking this as read, surely then any environment where light levels are the same or similar (under or over water) would be an evolutionary advantage, hence it cannot be taken as strengthening the aquatic ape scenario.