I have a shower stall with sectioned walls that leaks water while in use. The water comes out from the left front corner on the floor and leaves a large puddle. The shower was installed around 12 years ago. If I apply a heavy seal of silicone sealant around the shower drain seam, it seems to stop the leak for a while. Does this sound like the water might be coming from between the drain and under part of the floor? I haven’t found any hairline cracks in the fiberglass floor.
I assume the shower base is one piece and the walls are in sections. If you are applying silicone around the drain and stopping the leak, the leak must be in the connection of the drain line to the base of the shower. If you open the area below the shower base you can check for the source of the leak.
You can repair this by working from above and under the shower. Remove the shower drain and reinstall it with new plumbers putty or bathroom sealant/caulk around the tail piece connection to the shower base.
This is not always easy and it helps if you know what you are doing, so I suggest contacting a plumber. You may find corroded parts that need replacement. Your water leak problem could also be around the shower door or through the sides of the curtain.