Since they shelter us from storms and are capable of getting us home safely in a downpour, we never stop to think that a car is anything but waterproof. However, water damage can affect everything, including your car. Flood damage especially can cause trauma to your vehicle. If you have recently driven through high water, you may want to check your car for water damage and take the necessary precautions to keep it running efficiently.
The easiest way to tell if your car is suffering from water damage after a drive through some serious lake-like puddles is by checking the inside upholstery. If the carpet is damp, you will need to have the car looked at by a professional as this is an indication that your car's underside has been compromised. You could just let the carpet dry on its own, but you will probably wish you hadn't after that charming mildew along with its rank smell set in. Check the seat brackets for rust, as well.
Check your car's fluids. If the oil or transmission fluid appears diluted or milky on the dipstick, or has changed colors in some way, their holding pans are probably holding water. Hopefully you will already be aware of the original color of the fluids in your car. If you're not, try to educate yourself so you won't be at the mercy of ignorance when you want to ensure your car is safe to drive! If the fluids have seemed to change color or consistency, do NOT drive your car! Driving it in that condition can cause a lot more expensive damage. Have it towed to a certified mechanic. You should also check your air filter to see if it is wet or damp. If it is, replace it, and change the oil as well. The undercarriage of your car should be free of dirt, mud, or rust. Your brakes should be checked by a professional.
If you notice any condensation or water inside the coverings of any exterior lights, have them replaced. Use your ears to check for weird noises while your car is in operation, and if you notice something odd take it in to the car doctor, making sure you've told them where you heard the noise coming from, and what you were doing when it occurred (turning, braking, etc.). And please remember that even new cars who come with their joints "lubricated for life" should be checked up on once in a while for rust.