I feel at home in the ocean. I love to swim in it, scuba dive, and even live near it. Humans, however, are not built for the ocean. If you are curious like me you might be wondering if it is possible to see underwater. Can you open your eyes in the ocean and will it sting?
Can You Open Your Eyes in the Ocean?
The short answer is yes, you can open your eyes in the ocean. Clean ocean water is not harmful to your eyes. The salt stings a little, but this passes very quickly. Some refer to this as ocean water eye irritation.
You are however more prone to water-borne pathogens infecting your eyes. I personally have never had an eye infection and open my eyes in the ocean on a regular basis. This begs the question, is saltwater good for your eyes? Saline, after all, is one of the best treatments for eye infections. The catch is that saline is just water and sodium chloride, which is otherwise known as salt. The ocean has lots of bacteria and other substances in it. These have the potential to be harmful.
Our recommendation is to rinse your eyes after a day of snorkeling or scuba diving. This is how you clear the bacteria from your eyes and prevent them from causing eye infections.
How to Open Your Eyes Underwater?
The first few times you attempt to open your eyes underwater might be difficult. I remember having a reflex against opening them at first. So to start out, I recommend opening them really slowly in confined water. Squinting at first and then opening slowly one eye at a time. This will allow you to get used to it and manage the stinging better.
Can You Open Your Eyes in Chlorine Water
When we are talking about chlorine water, we are talking about swimming pools. Chlorine is used to stop bacteria and algae growth in swimming pools. While prolonged exposure to chlorine water is not great and some people can have a reaction to it, it is generally not harmful to your eyes.
Can You Open Your Eyes in a Saltwater Pool
Saltwater pools actually use a process called electrolysis, which turns salt into chlorine. These pools tend to smell less of chlorine and are generally favored as scuba diving pools since they are less damaging to scuba diving equipment. As for opening your eyes the same applies here.
Opening Eyes Underwater: Can You See Clearly?
Now that you know the answer to can you open your eyes in the ocean, you might be wondering what it looks like? From experience, I can tell you that opening your eyes underwater creates an image that is very blurry and appears brighter.
Consider the image on the left as seen with the naked eye underwater. It is blurry and it is difficult to make out any detail. The image on the right appears sharp and closer to the observer. This is the same scene observed using a mask.
Let’s not get too scientific as to why this happens. Basically a camera lens or our eye is able to focus by refracting light rays. These first pass through air and then through a liquid in our eye that functions as a lens. Light rays when passing from one medium through another change refractive index. This allows our eyes to prefocus an image so that we are able to see clearly in the air. A mask adds a pocket of air allowing our eyes to function in the same way. It does, however, distort the image, making it appear 33% larger and 25% closer.
If we attempt to see underwater with the naked eye, we lose the ability to pre-focus an image since seawater and the liquid in our eyes have virtually the same refractive index. This phenomenon is exemplified by the fact that light is absorbed underwater and our eyes need to widen their pupils in order to let more light in. Wider pupils allow the light rays to enter the eye at greater angles making the image even blurrier.
Michael Holcombe delves into more detail in his write up.
Interestingly there are humans that see more than twice as clearly underwater than the average person. These are known as the Moken people whom primarily inhabit the Andaman sea between Thailand and Myanmar. Moken children have learned to control their pupil dilation in order to focus light rays more closely resulting in clearer underwater vision.
Occasionally you meet Moken people during dive trips in the Mergui archipelago.
Watch more in this BBC segment below.
So there you have it, you can open your eyes in the ocean. The discomfort is temporary and if you rinse your eyes afterward there is very little risk of eye infection. Seeing underwater can help you during scuba diving training when you remove your mask underwater. A blurry picture is better than not seeing anything at all.