Why do we see blurry underwater?
First thing’s first, why can we see perfectly fine out of water, then vision gets all cloudy and blurry when we open our eyes underwater? Basically, science. Our ancestors didn’t really enjoy long underwater swims that much, and spent most of their time on land. For that reason, our eyes have adapted to view the best in air rather than water. How exactly so? Get ready for a huge science lesson.
When light rays travel from one medium to another, they bend. The amount of bending that they do depends on the ‘refractive indices’ of the two mediums. The greater the difference in the refractive indices of the mediums, the more that light bends as it moves from one medium to the other. Air has a refractive index of about 1, while our cornea has a refractive index of around 1.33333. Because of the difference in the refractive index of our eyes and air, light is able to bend before it enters the eye, pre-focusing the image before it reaches our lens. This is why we’re able to focus our eyes so clearly.
Water, however, has a much more similar refractive index to our cornea, also sitting around 1.3333. That means that light doesn’t have enough time to bend before it reaches our eyes, providing a more distorted vision. It’s quite similar to setting up a projector too close to the wall, where there’s not enough space for the image to focus.
The tribe that sees underwater
Here’s where it gets interesting. You could take all this information for gospel and subject yourself to a lifetime of wearing goggles and being unable to properly focus underwater. Or, you could take this incredible example of human evolution to be some inspiration that one day you, too, will be able to see underwater.
Younger generations of the Moken Tribe in Thailand are apparently able to ‘see like dolphins underwater’. The Moken is a small tribe that only needs simple tools like nets and spears for fishing in order to live. They dive for their food, able to go down as deep as 22 metres to catch a day’s dinner. And children of the tribe have been blessed with crystal clear underwater vision. Scientists aren’t exactly sure whether the children of the Moken tribe are able to see underwater due to genetic evolution or learning.
Can we be trained to see underwater?
To find out whether underwater vision could be learned, Anna Gislen from the University of Lund in Sweden carried out some research. She trained a group of European children for 11 sessions in Thailand, helping them develop underwater vision. After a month, the European kids saw significant improvement in their underwater vision, with their eyesight as acute as that of the Moken children.
That said, the European children all experienced red, irritated eyes due to the saltwater, while the Moken children experienced no ill-effects from the saltwater at all. This is where scientists are thinking that it’s likely the Moken children have developed something in their eyes to protect them from the salt. So we’d say that you could definitely improve your underwater vision and make it more accurate, but it might not be entirely pleasant for your eyes.
We’ll stick to the goggles for now
While the promise of crystal clear underwater vision sure sounds alluring, we think we’ll stick to the goggles here at Ninja Shark. Maybe we’ll take them off every now and then to practice our underwater vision, but the promise of red and irritated eyes hasn’t got us too excited.
What do you think? Will you try to train your eyes to have underwater vision like the Moken children?