Yes it's a coupe, rear hatch seal appears in decent condition, there are no wet spots in the trunk carpet area , the rear cubby pockets or the center well, but why do you ask ; is there a " connection " between the rear hatch and that footwell ? Sounds almost certain it's the drain tube considering RAP had the same problem.
Thanks for the tip Philippe, but I already knew the first step is to remove the engine, this is a 968 after all, that step is on the firstt page of the service manual as obligatory with any repairs, I just did that the other day before I replaced the windshield wiper fuse .