Puddle In rear hatch
I have a Trans Am, not a Camaro, but I'm assuming the interior hatch plastics are arranged similarly. Hope this is what you're requesting:
You need to get yourself a door trim panel clip removal tool:

Panel Clips:

Front sides have little fingers -- don't snap them off:

That's as far as I've ever gone with it.
If you've not already drained the water with a shop vac, I believe there are a pair of rubber stoppers located at the front of the bottom section of the trunk, underneath the carpet.
That same piece of weatherstripping was coming off at the front corner on the driver's side of my car. I glued it back in place with 3M Weatherstrip Adhesive.

