As marine canvas ages, it tends to lose its ability to repel water. Don't despair: You can refresh the material with a product such as Meguiar's Canvas Protectant (about $18.50 for a 21-ounce aerosol can) or Star brite Waterproofing with PTEF (about $20 for a 22-ounce spray bottle). Be careful when treating canvas that abuts clear enclosures, plastic or fiberglass because the chemical might mar the adjacent finishes. Also make sure the canvas is carefully cleaned before applying the new waterproofing. It might require multiple applications to bring back the desired level of repellency.