While you can physically open your eyes in the ocean, it is generally not recommended due to immediate discomfort and potential health risks. The stinging and blurring sensation is a direct physiological response to the water’s high salinity. Ocean water also harbors numerous biological and chemical contaminants that can cause serious eye infections or long-term damage.
Why Salt Water Causes Immediate Discomfort
The stinging sensation when opening your eyes underwater is a direct result of osmosis. The tear film covering your eye has a low salt concentration, but ocean water is significantly higher, creating a hypertonic solution. Ocean water actively draws moisture out of the delicate cells of the cornea and conjunctiva.
This rapid dehydration causes the surface cells to shrink, leading to burning, stinging, and temporary visual blurriness. The protective tear film, consisting of water, oil, and mucus layers, is also disrupted and washed away. This breakdown leaves the eye’s surface exposed and vulnerable to foreign particles and microorganisms.
Once the tear film is compromised, the eye begins to overproduce tears to restore its normal moisture and chemical balance. This reflex causes the eyes to water excessively after exiting the water, working to flush out residual salt and irritants.
Understanding the Biological Contaminant Risks
The risks associated with opening your eyes in the ocean extend far beyond simple salt irritation. Coastal waters, especially near urban or agricultural runoff, can contain various pathogenic bacteria, viruses, and parasites that pose a threat to ocular health. These contaminants are distinct from the salt and can lead to severe infections, particularly if the eye’s surface is already compromised.
One of the most concerning risks is the presence of Acanthamoeba, a free-living amoeba found in both fresh and salt water that can cause a severe, sight-threatening infection called Acanthamoeba keratitis. While rare, this infection is intensely painful, difficult to treat, and most commonly affects individuals who wear contact lenses while swimming.
Other harmful bacteria, such as certain Vibrio species, including the halophilic Vibrio vulnificus, can also cause serious keratitis and conjunctivitis if they enter the eye, particularly if there is a pre-existing corneal scratch.
Ocean water also contains non-biological pollutants that cause physical and chemical damage to the eye’s surface. Particulate matter, such as fine sand, silt, and decomposing microplastics, can physically scratch the cornea, creating an entry point for pathogens.
Chemical contaminants like the UV filters in sunscreen, specifically compounds such as oxybenzone and avobenzone, can wash off the skin and cause intense, immediate stinging and chemical irritation upon contact with the eye.
Microplastics are of increasing concern because they can cause mechanical irritation and may carry adsorbed environmental toxins into the eye. These tiny plastic fragments can contribute to ocular surface inflammation. Pathogens like E. coli, which indicate fecal contamination from sewage runoff, also pose a risk for general bacterial eye infections like conjunctivitis.
Essential Precautions for Eye Safety
The most effective way to ensure clear vision underwater is to use a physical barrier, such as properly fitting swimming goggles or a diving mask. These devices form a watertight seal that prevents contact between the ocean water and the eye’s sensitive tissues, avoiding osmotic irritation and contaminant exposure. Some protective eyewear also offers UV filtering, which is beneficial since the sun’s rays can penetrate water and cause corneal damage.
A strong precaution is necessary for individuals who wear contact lenses, as they should be removed before entering the ocean. Contact lenses can absorb water and trap contaminants, essentially creating a perfect environment to hold organisms like Acanthamoeba directly against the cornea. This significantly elevates the risk for severe, vision-compromising infections that are often difficult to diagnose and treat.
If ocean water enters your eyes, rinse them thoroughly with fresh, clean water or a sterile saline solution immediately upon exiting. This rapid flushing action helps wash away residual salt, chemical irritants, and potential pathogens. Avoid rubbing your eyes, as this can worsen irritation or scratch the cornea. Seek medical attention if you experience persistent pain, redness, or blurred vision.