Scupper problems?

The rear compartment of my Malibu Stealth 12 filles up with water, and it just sit in it toward the sterm, weighing down the boat. We're talking about quite a few gallons. This occurs even when there is nothing in the stern of the boat, at all. It seems to be sloped to the rear and not allowing it to come out of the scuppers which are toward to front of the compartmentI carry only half the weight recomended for the boat, including my own weight.

I was wondering if anyone else has the same problem with their stealth.

Also, it always feels like I'm sitting in a puddle when I'm out, and was wondering if there were 1 way scupper plugs I can put under my seat?
Any paddle drip or water picked up launching in the surf can be able to drain out, without water coming up the scupper