Opel Astra 2001

Hello! The floor on the back drivers side of my 2001 Astra is absolutely soaking wet. It happened one day that my car was flooded with water in the back of the driver seat aswell in the front to the pedals First the amount of water was big enough but after the sponge from the back of the pasanger seat and the floor sponge that is underneath got soaked with water. Its imposible for me to sqweeze the water from the sponge. Now its not leaking from nowhere its just the water that remained in the sponge. My question is how is that possible to find myself flooded with water only in the back and front of passager seat. Its seems that all water came from the back of the driver seat on the floor. What should i espect next that is going to happen? is this going to damage my car in the near future?