I had the water in the tail lights problem (posts are water in trunk, leaky trunk)and found the 3M windsheild gasket (the black sticky gasket comes in a long flat roll) stuff works awesome. Many on this site talk about caulking or silicone - caulking didn't work for me and I spent 3 hours scraping it off - not fun.
For all your water leak needs, do it right the 1st time, go with the $10 roll of 3M available at your auto glass store.
That's what I learned and figured out.
