2003 Toyota 4runner SR5 4WD. Under my rear seats the floor board is all wet.

Are you sure it's coming from the rubber plugs? Water never comes up through the floor boards unless they are thoroughly rotted out. I would dry it and give it the old hose test from underneath. I would also check the rear wiper area and the brake light in the top of the rear door for leaks. If it is coming up through the floor, go to WalMart and buy that black rubber sealant called Flex Seal. Spray a good thick coating of that on those rubber plugs. It will be way cheaper than trying to find a set of new floor plugs.

Thank you! After more investigation The leak is coming up from the cargo area and then leaking into the rear area. The are for sure now is in the far back. I have an appointment next week to have them put my car on a lift and see if anything is visible from under the car. I cannot see any water that is coming in but I am going to look in the areas you mentioned above. THANK YOU!