Crying is a biological function involving the production of tears by the lacrimal glands, a process that continues regardless of the surrounding environment. While the physiological mechanism of tear creation remains active, the visible manifestation of crying is dramatically altered when submerged. The surrounding water instantly mixes with the newly formed tears, preventing the distinct tracks seen on land.
Understanding How Tears Are Formed
Tear production, medically termed lacrimation, is managed by the lacrimal apparatus, which includes the main lacrimal glands situated above the outer corner of the eye. These glands constantly secrete a complex fluid to maintain eye health and moisture. The fluid then spreads across the eye surface with each blink before draining through small openings called puncta, located near the nose.
Tears themselves are not simply saltwater; they form a three-layered film coating the eye. The innermost mucus layer helps the tear film adhere to the eye’s surface. The thick middle aqueous layer, primarily water and electrolytes like sodium and potassium, lubricates and nourishes, and contains proteins and antibacterial enzymes, such as lysozyme, which help fight infection.
An outer lipid layer, secreted by the meibomian glands along the eyelid margin, prevents the aqueous layer from evaporating too quickly and maintains a smooth optical surface. The body produces three main categories of tears, all of which continue to be generated when submerged. Basal tears are secreted continuously for lubrication and protection. Reflex tears are a rapid-response flush to irritants, such as dust or chemical fumes. Emotional tears, triggered by strong feelings, contain slightly different chemical components, including stress hormones.
What Happens When Tears Meet Water
The reason crying is not visually obvious underwater relates entirely to fluid dynamics and the absence of air. On land, a tear rolls down the cheek because it is a distinct, viscous fluid moving across the air-exposed skin. The visible track is enhanced by evaporation, which cools the skin and leaves behind a slightly thicker, saltier residue.
When a tear is produced beneath the surface, it immediately enters a medium that is already 100% humidity. The surrounding water prevents the rapid evaporation necessary to form the characteristic visible trail. Without this difference in surface tension and evaporation rate, the tears cannot maintain their shape or distinct path.
Tears are composed of approximately 98% water, giving them a density and viscosity very close to that of the external water. While tears are slightly more viscous than pure water due to proteins and mucin, this difference is negligible when submerged in a large volume of liquid. This similarity means the tear fluid does not remain a separate bead; instead, it mixes and disperses with the surrounding water instantaneously, effectively diluting the tear’s components.
The external water pressure also affects the normal drainage route of the tears through the puncta and nasolacrimal duct. While the drainage process may be slightly inhibited, the lacrimal glands continue their function of production. The underlying physiological mechanism is unaffected by the submersion.
Salinity, Osmosis, and Eye Irritation
The stinging sensation often felt when submerged is frequently mistaken for the physical sensation of crying, but it is actually a chemical reaction involving osmosis. Tears are naturally saline, containing electrolytes at a concentration of about 0.9%, which is isotonic with the eye’s surface cells. This balance is optimal for cell health and comfort.
When the eye is exposed to freshwater, which is hypotonic (lower salt concentration), water rushes into the cells of the cornea and conjunctiva to equalize the salinity. This influx causes the cells to swell slightly, leading to burning, blurry vision, and irritation. This cellular swelling is a direct physical response to the osmotic pressure difference.
Conversely, exposure to seawater, which has a higher salt concentration than tears (hypertonic), can draw water out of the eye cells through osmosis. This dehydrating effect also causes irritation, signaling the cells are under stress. The eye’s natural response to this irritation is to produce reflex tears, confirming that the sensation felt is usually the body reacting to the water, not sadness itself.