Water leak under rear seat

[DaveLiquid182]

Last week there was a small puddle under the rear seat. I thought nothing much of it and wiped it up.
This morning ive taken the rear seat out and there was loads of water
Anyone got any ideas?
I do remember a long time ago a mate of mine had this problem but that was from new. That was the wheel arches which was a problem for a few cars. Mine is 5yrs old and has just started

Oh and ive done a search but nothing really helped.

Cheers

 

[dunganick]

I would check the seal around the rubber stoppers next to the rear lights (when the tail gate is open)