The rest of the shower looks like brand new. December 22, 0 found this helpful. Epoxy already mentionedwater-proof caulk, and I also think there is a JB weld for plastics found in most Ace Hardware stores. Look on your RV websites, they have repair kits for plastic showers one is by SYONthere's one for fiberglass as well. It depends on how big the crack is. I have duct taped it, but that is only a stop gap.
They also make a similar product called Flex-Seal for lighter applications.
How to Repair a Crack in Your Shower Base
By cpgial [1 Comment]. I used flex shot and did not solve the problem with the cracks. Just Google it and check out their forums. I use this to repair leaky roofs. Refer to the instructions and allow the gelcoat to completely cure. Turn on the water and rinse off the residue and cleaner. Clean the shower pan thoroughly with a liquid bathroom cleaner and a bristle brush.