FACTS ABOUT MARINE FABRICS
Avoid Cheap fabrics like canvas duck won't hold up to long term sun exposure. They offer shade but they are not treated to block UV rays.  Most will leak as soon as the weave is stressed.     

White vinyl is the most popular choice because the color is universal and it is the least expensive waterproof fabric.  Marine Vinyl's' are easy to clean, but they range up and down in quality. Be sure to check the weight per square yard. A 24 oz. per sq. yd. Marine Vinyl is very durable and what you should expect in a better made top.    

Marine acrylic fabrics are used for many Bimini tops. "Sunbrella" is the best known marine acrylic fabric. It is a top line solution-dyed fabric. This woven fabric looks and feels good. The fabric is designed to allow some stretch as it is sold mostly to top shops for custom work.  It holds up well to UV rays and has exceptional fade resistance and strength. However, as it ages, it tends to stretch, sag and gradually start leaking. Better acrylic fabrics have 5 year warranties and cost more.    

Marine Polyester fabrics do not stretch . When solution-dyed, the fabric will not fade and the fabric color looks rich and holds up very well to UV sun exposure. Polyester fabrics are strong and retain their shape. Because Polyester wont stretch, it can be coated with Urethane to provide a truly water proof marine fabric. High quality Polyester fabrics resist mold and mildew, are solution dyed and water proof. They are warranted for 5 years and I think they offer the best fabric for marine use.