Water leaking, no seals?

Just had to remove the noise cancelling foam as it was soaked.
After few trials, some of the water was gaining access to the boot through the air vents (don't know the correct name for it, sorry) between the rear wheel arch and the rear bumber. Seems like the flaps from the air vents can't hold the water if there's a lot of it going through. Removed, cleaned and sealed around, problem partially solved.
When removing the rear tail light cluster (driver side), I just realized that there isn't any seal. The water runs freely behind it. It's normal? Checked the passenger side, and the same, no seal.
Just removed the boot seal, and gave it a good clean. Water still gaining access from the tail lights, can't see from where exactly.
Any ideas?

Thanks for the input. As you mentioned, never had a car where it's designed for the water to run behind the light cluster. Today, after yesterday's rain, same problem, less water in, but was some water, despite removig the rear bumper, sealing the air vents inside and out, removing all grommets, cleaning and sealing. Tried pouring a lot of water, was dry. Rainning now, let's see if it's sorted.

Same problem, again.
After removing the rear bumper, sealing around the trunk vents (or flaps, don't know how to call them, sorry), and giving the rubber flaps a good clean, I had about 3 months problem-free.
At the same time, I had removed the boot seal, gave it a good clean and carefully put back in place. 3 days ago, after washing the car, I did notice some water (a little, but it's starting to happen again), accumulating behind the driver's side back wheel arch.
Any ideas to pin point the problem without going to the expense of replacing the vents and the boot seal?
Is there any chance that the water may come from the fuel flap? I had it replaced about a year ago, and the drain is unblocked, as it's supposed to be.
Any ideas?

Nope. Just a regular sc. Panoramic sunroof usually drains. But mine, so far, no clue.