Water-resistant, water-repellent, and water-proof are technical terms used to describe how dry a material will remain when subjected to rain. Water-resistant means water is prevented from penetrating up to a certain point and water penetration is delayed but not prevented. Water-repellent fabrics are a step better and are designed to shed water, but will soak through in a heavy downpour. Water-proof barrier fabrics such as vinyl are nonporous and can't be penetrated by water even in the heaviest rain. Occasionally terms such as "water-proof (highly water-resistant)" and "virtually water-proof" have been used to describe fabrics, but these terms are highly misleading and technically incorrect. They are terms whose sense in common usage conflicts with technical sense. Most marine fabrics including superior marine canvas, acrylic polyester, and treated canvas are all woven fabrics with interstitial spaces (gaps between fibers). Regardless of the brand, treatment, or finish, superior marine canvas, acrylic polyester, and treated canvas are not water-proof. Superior marine canvas is water-repellent. Acrylic polyester is water-repellent. Treated canvas is water resistant. Water-repellent and water-resistant fabrics exposed to standing water or extended periods of rain will drip through and become saturated over time. For these reasons Brinmar uses only industrial vinyl because it offers the ultimate water-proof barrier and the absolute maximum protection against moisture.