Meguiar's, Duragloss and 3M are all companies that have a marine line.
FWIW, In over 30 years of boat ownership, I used the same products I was using on my vehicle in most instances.
The only marine line that I used was Meguiar's and while it worked good so did most everything else I used.
The one thing that I never had to do was actually compound my boats. I polished/waxed them each year and they never really needed it.
Gel coat does seem to be much harder than paint.
The past two years I used Optimum Poli-Seal to clean and polish, then used Optimum Opti-Seal for a sealant. The boat was on a lift under a canopy, but wasn't completely protected from the elements. The Opti-Seal seemed to hold up quite well.
Based on my esperience with the Duragloss #501 Marine Polish and Sealant on vehicles, I would probably try it if I still owned a boat. Great one step product.