Pontoon boat sealer?

I know this is an auto detailing site but I figured you guys would have the right answers instead of listing to the wanna-bee's at the marina.

My brother-in-law has a beautiful Bennington pontoon boat, after leaving it in the lake all summer the pontoons got pretty nasty. The local yokel marina guy sold him some cleaner for the pontoons, it was an acid based product. Sure it cleaned them up nice but it also took off all the shine and left a white looking residue. He did every thing right according to the directions, but they look bad.

He's now polishing them out using a rotary with a wool pad and some cheap walmart compound, they actually are starting to look good.

My question is, what should he put on the pontoons after he's done polishing them to seal them for next season? I'd hate to see him and my sister go through this again.
Thanks

Gel Coat Labs All Marine Surface Sealant is my go to for boats. It is made by the same guys who make Ultima and Four Star

Is the problem area above or below the waterline? I don't think any kind of wax or sealant will last all season below the water line. If it is kept in the water all season, it should have the bottom painted. As far as above the waterline, Collinite makes some great stuff, and Rejex has some great reviews also.

The pontoons are made of aluminum, so basically I need a polished aluminum sealer.

Toon~Brite google it it's the best we have found

Toon Brite is the stuff