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We parked our CS23 under a couple of huge Oak trees this spring. The yellow, stringy pollin fell on the boat and left nasty stains all over the swim platform! Dawn soap won’t touch them… and they’re ugly! Any ideas on how to remove them? Thanks!

I've always had decent luck with 303 products - something like https://a.co/d/09oBHpZ4
I haven't used marine 31, but have also heard good things about their cleaner - https://marine31.com/marine-31-vinyl-cl ... ioner.html

and some people use Dawn mixed with a little vinegar or a little bleach and say it works better. I don't know what's on your swim platform, so you may have to experiment a bit.

Hi,
Lots of things to try but let's start with the easiest. You've cleaned the cause of the stains, let the swimstep sit in the Sun for a few days before trying some of the more drastic approaches. The Sun can bleach out pollen stains, boat yard blues and sap stains in time.
A safe addition to the soap and water of white vinegar could do the trick as it ups the pH a bit. use a mild mixture of white vinegar and dish soap, Using distilled water mixed with a little oxalic or an oxalic acid-based cleaner like Bar Keepers Friend. (follow instructions)
Shy of that, on smooth gelcoat, use a mild "cleaner wax" (never a "restorer wax") and a terrycloth towel. Work the stained gelcoat by handand see if there's a difference. Don't use a machine, heat in a specific spot is not what you want.
Using a product like Bon-Ami or a scouring powder with bleach will require a repolish of any shiny gelcoat touched in the process. Products like "FSR" can be applied or a gel bleach (kept damp, don't let dry) would be in the extreme. In the most extreme, a toilet bowl cleaner, kept wet, never allowed to dry or lay on colored gelcoat. Apply with a brush (wear gloves) let sit for a bit and then rinse thoroughly and let dry. The chemical reaction might take a few hours. You'll want to rewax any smooth gelcoat this stuff touches. Don't be stingy on the rinsing. Don't let this dry up on your boat.

Try to remember that gelcoat is porous and stains can run deep. Scrubbing "till its gone" will inevitably remove gelcoat. If you can remove the surface contamination and allow surfactants or UV radiation to dive deep into the substrate before trying to dig it out.