on the 1st pic you can see the white bit right at the side of the boot seal , this is the old flexi seal thats gone hard and bristle and is now letting water past
the 2nd and 3rd pictures are arrowed , these arrows point to a metal flap inside the boot, it must be were the boot meets the rear quater
water is getting in there and running around the flap (arrowed) and into the boot


