You can absolutely get a sunburn while underwater. This common misconception that submerging yourself protects your skin often leads to unexpected burns. Sunburn is damage inflicted by overexposure to ultraviolet (UV) radiation, and water does not block these rays entirely. Even when fully submerged, UV rays penetrate the water’s surface, exposing your skin.
How UV Radiation Travels Through Water
Solar ultraviolet radiation is categorized into two types that reach the Earth’s surface: UV-A and UV-B. These different wavelengths interact differently with water molecules and suspended particles, which dictates their penetration depth. UV-B radiation, the primary cause of sunburn and surface skin damage, is readily absorbed by water, with approximately 50% absorbed within the first meter of clear water.
The longer wavelength UV-A radiation penetrates much deeper into the water column. UV-A rays are less efficiently absorbed by water and can reach significant depths, sometimes over 50 meters in clear ocean conditions. This deep penetration means that even when fully submerged, your skin is exposed to UV-A, which contributes to long-term skin aging and damage.
Key Factors Influencing Underwater Sunburn Risk
The degree of risk when submerged depends on specific environmental and physical variables. Depth is the most straightforward factor, as UV intensity exponentially decreases the deeper you go. However, in typical swimming depths, such as a pool or near the surface, UV exposure remains substantial; up to 40% of surface UV radiation can still reach a person just half a meter below the water.
Water clarity plays a significant role in how much UV light is attenuated. Turbid water, which contains sediment or pollution, absorbs and scatters UV radiation more effectively, reducing penetration depth. Conversely, clear water allows UV rays to penetrate to greater depths, increasing the risk for submerged swimmers.
The reflective nature of the water’s surface is another factor that increases exposure for individuals swimming just below it. Water reflects about 5% to 10% of UV radiation, and this reflection, combined with direct sunlight, amplifies the total UV dose received near the surface. This amplification is why people often burn faster when near or in the water.
Preventing Sunburn While Submerged
Effective protection requires a combination of behavioral changes and specialized products designed for aquatic environments. Always use a broad-spectrum, water-resistant sunscreen with a Sun Protection Factor (SPF) of 30 or higher. Apply sunscreen generously to all exposed skin at least 15 to 20 minutes before getting into the water to allow it to bond with the skin.
Reapplication is equally important, as water-resistant formulas still wash off or degrade over time, with most needing reapplication every 40 to 80 minutes while swimming. Applying a thick, zinc-based formula to sensitive areas like the face, neck, and shoulders can provide enhanced protection.
Wearing protective clothing is a reliable strategy. Garments with a high Ultraviolet Protection Factor (UPF) rating, such as rash guards or wetsuits, block UV rays effectively, even when wet.
Limiting time in the water during peak UV hours is a powerful behavioral adjustment. Since UV intensity is highest between 10 a.m. and 4 p.m., avoiding swimming during these times significantly reduces the overall risk of skin damage.