2006 volo s40

wondering if anybody else ran into my problem, water leaking in from somewhere and fill up passenger rear well, not a little but a lot! not my car, (I owe a chevy) so I got the story that when it rains , and when the air condition is on that when it worst, I remove the seat and gave it a five minute water test , nothing, and I put the hose everywhere,
what do you guys think?