100% Natural, Biodegradable, Chemical-Free, Reef Friendly sunscreen lotion that blocks all UVB and UVA rays. This is a sun block for those who are not as active in the water as those who would use the SolGuard spf 25. Though it still is a complete UV block and has all the ingredients as the SolGuard spf 25, there is a little less Titanium Dioxide and Zinc Oxide used. Though there is no UV ray penetration when using SolGuard spf 15, you will experience a slight darkeing of the skin due to the heat promoting our own melanin to darken the tissue over time. It is water resistant and will not come off upon entry into the water and needs not to be rubbed in when applying to the needed areas of protection. Gently wipe the lotion on the body area needing protection and let the moisturizers penetrate the skin to provide hydration, while the natural minerals reflecting the UVB and UVA rays remain on top of the skin. Pay special attention to areas whre the bone is closest to the skin such as the shoulders, the face, tops of feet, and bathing suit lines, as these areas seem more prone to sunburn. Apply ever hour to hour and a half for best results. No parabens are used to preserve the sunscreen. Thers is a 24 month shelf-life to these sunscreen products.