Clean the shower using a diluted bleach solution to get rid of any residue or mildew. Rinse the shower and dry thoroughly. Work a towel into the damaged area or use a blow dryer to ensure it is dry.
Place a tube of mildew-resistant acrylic sealant into a caulking gun. Cut off the nozzle tip and insert a nail into the nozzle to release the sealant.
Press the nozzle into the start of the crack or damaged area and depress the plunger to fill the entire crack.
Wet your finger and wipe it over the sealant to smooth the surface and lift off any excess sealant. The sealant won't stick to a damp finger.
Allow the sealant to cure for 48 hours or as recommended on the package instructions.