My 91 Camry started leaking water into the driver side about 10 years ago, and into the passenger side about 3 years ago. The cause looks to me like a design fault. The channel under the wipers drains out a hole in each side (behind the side panels over the front wheels). These drain holes have rubber flaps, presumably to stop dust getting in. What happens is the flaps obstruct the drain holes sufficiently to trap organic material (leaves etc) that has made its way into the channel. After some years the organic material causes the channel to rust through, letting water into the inside of the car. To make matters worse, the water enters directly over some important electrical stuff - junctions, fuses and relays.
I believe, but can't prove, that this is the cause of a frustrating intermittent problem that I have. Although I've done what I can to stop water coming through (various measures that I will not elaborate on unless asked), the car has a fault in the ignition system that sometimes stops the spark from happening. This usually occurs on trying to start the car, but a couple of times it has failed while the engine was running. The failures are unrelated to the weather, and recently have happened when it's been dry for weeks. All electrical tests I've carried out show OK. This has been plaguing me for couple of years. Usually the car restarts within about half an hour, but not always. A mechanic replaced the distributor, but that didn't change anything. The error code is 43, which refers to the starter signal STA, but that doesn't really make sense since the engine cranks and there is always 12 v at the distributor.