To offer some accurate advice:

Check your trunk seals, door seals, window seals, etc.  Then put on your thinking cap.  Leaks in engine compartments just don't happen: the engine is open to the elements anyway.  So, look in the trunk.  More times than I want to count, I have found Japanese and Korean cars that don't have low-point drains, so water accumulates in the low spots, causing rust that will definitely put your car in the body shop for a ton of money.

The solution is to find the lowest spots (usually behind the rear wheels) and drill a 3/8" hole through the inside body metal to allow the water to drain properly.  DO NOT RE-SEAL THE HOLES!!!!!  You want adequate drainage. 

If you run out of leaking body seals, get a gallon of "water fink," shut the doors and roll up the windows, then pour the water fink over the car.  It is clear.  Once you have poured it, let the outside drain a few minutes.  Then open the car doors and trunk to see where the water went.  Use the provided Ultraviolet light.  It shows up brilliant orange.

Hope that helps.