Sealing natural stone and masonry materials exposed to the elements, especially around a swimming pool. is critically important to protect the structural integrity and maintain appearance. . Prolonged exposures to sun, water, dissolved organics and chemicals stain, erode, crack and fade stone surfaces in and around your swimming pool soon after installation. We recommend sealing your stone when new; however if the damage has already occurred; Let Watermark Pros restore and protect the beauty and integrity of your exterior stone surfaces.