Maybe a fiberglass paint? Something that would work in a marine environment would work here I think. Boat paint.

Have you tried plugging the drain and covering the floor with paper towel and soaking in white vinegar?
Linda C

You can make scouring powder by mixing four parts baking soda and one part washing soda.

Ive had good results on some really bad fiberglass shower floors using The Works T-bowl cleaner and a scrub brush. Squirt some on the floor add water and scrub with a long handled kitchen brush. Then rinse good.

Make sure you test a spot. Ive never had a problem but you never know. Also dont leave it on too long before you rinse. And be sure to vent. The fumes will get you. PHEW.

Sometimes the floor finish is so worn that the undercoat is showing. In that case forget it.

Home Depot has recoating kit for fiberglass showers and tubs. Ive never tried it but you might want to check it out.

Wet the floor & sprinkle 20 Mule Team Borax on it...allow to sit a few minutes and scrub with a brush. I used it on our grungy looking old bathtub (which had been refinished some time ago) and was totally amazed! Does a fabulous job on laundry stains too.

In case you're wondering (since I suggested this product for floor cleaning in response to another post,) I am not affiliated with the company nor do I own stock. ; )

Suzi

Cascade or other dishwasher powder, sprinkled on the floor of the shower (wet it first). Let it sit half an hour or so and scrub with a good brush. Works for me!

I used a Mr. Clean Eraser on mine and it now looks like new. I understand the floor is made that way to make it non-slippery, but what a nightmare to clean!

I used Bar Keepers Friend with great results.

I use that foaming Bubble spray on mine. Spray it good, let it sit a while and then use a long handled brush to scrub it. Works good on mine.

When I moved into my current place, the fiberglass shower had several years' buildup of soap scum. Guess the previous owner wasn't into cleaning. I have never used bar soap, only liquid, so getting rid of it was something I never had to do before.

I tried *everything*...barkeepers friend, different bathroom cleaners, vinegar...nothing and I mean nothing would cut it. It was ugly for a couple years until one day I was cleaning the oven and realized that if oven cleaner could cut baked on food, it might work on the soap scum.

I did a little patch test to make sure it wouldn't hurt the fiberglass, and then sprayed a section. Let it sit for 15-20 minutes and the scum came right off. I still had to use a scrub brush, but it pretty much lifted right off.

The only problem was the fumes. My bath is really small and doesn't have a window, so I could only do small sections at a time to avoid being gassed out, lol. But it did the job and now my shower is shiny and glossy again.

Of course, keep it away from the metal fixtures because it will damage the surface. And do a little patch test in a dark corner to make sure it won't harm your finish.

Just go to Home Despot and read the instructions on the Home Despot fiberglass refinishing kit. If anyone should know, the people who write the instructions on how to use the kit should know.

You will never try anything else after this... I use a tile and vinyl cleaner made for swimming pools. Just sponge on, wait 5 or 10 minutes, lightly scrub with a magic eraser sponge, and rinse. Pool stores don't all carry this stuff, but you can buy it online. I like Blue Wave tile and vinyl cleaner, and NWS tile and vinyl cleaner. They both work well.

Thanks so much to all of you for your helpful suggestions. After months of frustration and knocking myself out with different cleaning applications to no avail, I finally came up with the answer to that horrible floor. Yup, a whole new shower! We removed not only that sorry-looking shower pan, but the old tiles on all three surrounding walls. As I type they're installing beautiful new slate tiles!

I have a 28 year old tiled shower with a fiberglass floor and it looked every bit of 28. I tried many different types of chemical cleaners and vinegar, bleach, scrub brushes, etc. But, it never looked clean, always worn and dirty. Today, as I filled up the base with water, I sprinkled in 4 scoops of OxyClean, stirred it a little and then let it sit for over an hour. Before I drained it, I rubbed it down a little with a scronge, and Holy Cow!! does it look clean. Not only clean, but it looks new. Billy Mayes would be proud. LOL

OMG! I had tried everything and given up. Same problem...brownish gray stains in the fiberglass that wouldn't bleach or scrub out. Then I read the suggestion to sprinkle borax and scrub and had also read somewhere to mix borax and baking soda and scrub and so I sprinkled the borax and baking soda mix and scrubbed a big circle area and for the first time in years I can see a bright, clean shower floor! Is going to take some scrubbing, but scrubbing and seeing results is way better than scrubbing and nothing happening. Thank you grittymitts, thank you Borax!

Try Fantastic spray. I don't if it will work, but if the problem is soap residue it should clean it.

I had a fiberglass basement shower that was absolutely disgusting when I moved into my new house. I tried everything, and I do mean everything. I got a tip from here about using Easy Off Oven Cleaner (in the BLUE can.) I spraying on an entire can, closed the door (cause the fumes are horrible) and came back in an hour to a completely CLEAN shower stall. All I had to do was wash it off. CLEAN!

I totally recommend this is as the lazy girl's guide to a clean shower.

After reading all the above and trying several, just have to say none really worked....sooo, I happened to have a product called Goo Gone (which can be purchased most anywhere, Walmart, etc.)....it is a solvent, so I tried it....squirted it all over my vinyl shower floor....let it stand about 30 mins. and scrubbed it w/a scrub brush....it got most of the stubborn film off the first time....had to do a few spots the 2nd time....it's the ONLY thing that really worked well.

DAWN dishwashing liquid in a bucket of hot water, wiped on the shower with a good rough washcloth. Works great!!

I reasoned that Dawn is the best at cutting grease on dirty dishes - why not oily soap scum on a shower?

This is my husband's shower, and he refuses to use anything but bar soap.

What is preferable to bar soap?

I am not a chemist so I don't know all the proper terminology, but I understand that bar soap is the worst for soap scum - something about the ingredients necessary to make the soap bind itself together into a bar. I assume it's some kind of oily compound.

I use only liquid body wash (in a bottle) - never bar soap. But hubby won't budge from his favorite bar (Safeguard).

The SOS pads work very well at getting all the soap scum and hard water stains clean. Another great option is the Mr. Clean magic erasers. Either of these should do the trick.

I've tried everything mentioned except the googone(toxic). EasyOff(toxic) Don't use commercial stuff like Fantastic...only vinegar, baking soda, bonAmi,etc.
I third the borax and oxyclean.
What has recently worked for me is taking a wet cloth, i use the wash cloth type cotton shop cloths that are nubby. sprinkle on a heap tblsp of borax or oxyclean, then a splash of peroxide and wipe down the wet shower pan. Leave the cloth behind and return 10-20 minutes later and re-peat the process while also wiping down the glass shower doors and tile walls. Later, just before i shower i hose it off with a hand held shower head and wipe it down with a wet clean cloth. I've heard to wipe down with baby oil or mineral oil will help between cleanings but have not tried that. (on the glass only)
I might try my coconut/h2o mix i keep in the shower as a body rinse and finish rinse for my dogs.
Could sir in a bit of cornstarch to the pexoxide and heat for 20 sec in micro to make it a paste, then add the oxy...
cover with plastic wrap and let sit for 24hrs for a weird staining. Not tried it but heard it needs uv light and is said to work on yellowed plastic like old white cuisinarts and sewing machines.