I also have a 2008 cruiser I purchased a few years ago. I suspected water under the cockpit floor so I added a 4" removable inspection plate near the stern on the port side of the center stringer. I think one inspection point is enough since the center stringer does not extend the full length of the floor so water on one side will also be on the other. There was water under the floor which I dried quickly with a small fan placed in the inspection port. There were multiple culprits: The vertical fiberglass gas tank covers were screwed directly into the floor (non-cored area), the screws were loose or missing so the screw holes allowed water in. There were several items screwed down in the bilge that may have leaked (I relocated all of that). And finally, as mentioned before, the gap between the cockpit floor and the cabin needed resealing. Since fixing all that the space between the cockpit floor and hull has remained dry.
My cockpit floor did not feel spongy. It is cored with balsa so look for any place the fiberglass skin has been punctured with screws. Check for moisture there. My boat had some added, larger steps on each side that were screwed to the cockpit floor. I removed those and found minor moisture issues around some of the screws. None of the screw penetrations were bedded correctly.
Enjoy your boat! I love mine.