For the last few years I've been using this Pittsburgh deck sealant/revitalizer. The stuff is very cool. Acts almost like the spray-in truck bedliner stuff. It's very thick - fills cracks up to 1/4" (3 coats) and makes my 30 year-old back deck look like a new composite deck. Water can stand on it. We use it on the decks, docks, concrete porch, woodpile roof (heh) and I even just finished covering my outdoor sub-woofer enclosures with it as they were showing their age in the weather. Stuff even has sand/grit in it for anti-slip and good wear resistance. I know other manufacturers make similar stuff but your mileage may vary.

