If you have been running your air conditioner, it's possible that your drain hose is clogged, and the condensation is dripping in.
It is also possible that you have a leak in the heater core or a windshield leak.
In the trunk, underneath the floor-cover, on the passenger side.
Are you running the air conditioner? If the drain line is plugged, it will leak water (condensation) onto the passenger side floor.
it is on the right side of the trans. between the trans. and the passenger floor underneath the car
sounds like there could be a plug knocked out of the firewall on the passengers side which would allow water to enter when you hit some puddles and splashed up
A leak on the passenger side floor of your BMW Z3 could be caused by a few issues. Common culprits include a clogged or damaged sunroof drain, which can allow water to overflow into the cabin, or a faulty door seal that permits rainwater or moisture to enter. Additionally, a leak in the windshield seal or a bad heater core could contribute to water accumulation on that side. It's advisable to inspect these areas for blockages or damage to determine the source of the leak.
Dry up the water. Take the car to a car wash and spray it good around doors and windows. If a leak is not visible then check the floor during rain storms while driving to see if water is coming in through a leak in the floor.
heater core may be leaking or hole in floor
Is it blood, oil, water, or urine?
There is a drain on the outside firewall that is clogged.
you could have a heater core leaking or your windshield is leaking and the water is running down behind the dash and onto the floor.
Probably have a leak in the heater core>
Heater. Core