Wet feet

[hammerboy]

I have water in the footwell, passenger side, no obvious leaks in the body work, what could it be?

[eltelioni]

Leaking engine coolant - it would be warm.
Leaking screenwash - you would smell it.
Condensation from air-con - it would be pure and clean.
But most likely perished or damaged rubber in the gullies and pipes that channel rainwater from the air vents at the bottom of the windscreen to the underneath of the car.

[Hymie]

A common fault on many modern cars is that the drain hole in the air filter housing (within the engine compartment) blocks. As a result, the housing fills with rain water and eventually empties into the passenger cabin. Whether this is the cause on your car, may well depend on the car model/make.

[johnny37]

I had this in my Focus, even posted a question. After a lot of worrying it turned out that the seal round the windscreen on the passneger side had come unstuck. In heavy rain it was running down the windscreen inot car.

[Jackson74]

Faulty Heater matrix in my experience!

[anotheoldgit]

As said before, blocked drainage holes under the bonnet air vents. These can be cleaned by pushing a thin bar down the hole. (a welding rod is ideal).

If you have a sunshine roof there are drainage holes for this also.

[Chasingcars]

I had the same problem on 2 cars. In my first car, I had soggy front passenger foot well- it was Air conditioning - though dont get me to explain what caused it!
Second car, the rear window was replaced after accident and the seal wasnt sealed properly and water came in and sat in the rear pasenger foot well :(

[wullybaxter]

seal round passenger door may be the problem. Roll down passenger door window put knee against inside of open door and pull window frame in wards , that will tighten seal

[santaponsa]

the dain holes in the sills.
I had this problem with a Clio