SolRx WaterBlock sunscreens are a high performance sun care line that is dedicated to athletes, competitors, and active lifestyles. SolRx sunscreens use an exclusive WaterBlock technology offering extended protection. This is a superior sunscreen that is non-greasy, oil-free, reef-friendly, and does not wash off in water. SolRx WaterBlock sunscreens average 98% SPF retention after the industry standard 8-hour immersion test. Apply sunscreen liberally on dry skin 15-20 minutes before sun exposure. Reapply after 80 minutes of swimming or sweating, immediately after towel drying, and/or at least every two hours.