Like most of you guys, I had this problem in my 96 LS. I just got the car a few weeks back, I knew of the water problem so I tried some of the "quick" fixes first. I had water in the trunk. rear seats were soaked, and the head liner had water pooling above it....
Made sure the moon roof tubes were intact and in the right places...check
Checked the tail light gaskets? Not too bad, but still replaced them with higher quality material from Home Depot and they seal tight...check.
Cleaned the pine needles in the hatch thinking the water in the headliner was from that...check.
Ok fast forward two weeks into torrential Oregon downpours and more water.
I gutted the entire rear interior
And found some pooling water;
So with the interior out, I hooked the hose up and let it wash over the car while I sat inside with a flashlight...I immediately had droplets dripping on my head...
#1) The rear windshield sprayer seal was leaking...so that came off and is sealed (don't use it anyway)
#2) This was the big one where the majority of water was coming from.
Below the tail lights there is a hole below the wire harness and in this case, has a rubber plug in it preventing water from entering...
However on the passenger side, there is no plug and it's an open channel for water to literally FLOOD into the rear of the car
I'm looking now to find the part number and order a new plug from Acura, but I may just silicone it up too...Not sure.
How this helps someone out