Water in car
 

Hello need help ASAP
i have Audi A6 avant 1.9tdi 2003
there is water in the back behind passengers seat
i have checked drainage holes under battery and they are clear
car is now starting get some electrical faults such as indicators not turning off and the buttons on key stopped working de to water getting in ECU box under passenger seat
Please any suggestion or vids to watch
HELP