We all know to avoid flooded vehicles at all cost, however many of them are sold as normal cars and when they look clean, smell clean, and run good our doubt of having problems with the car is diminished. And flooded car doesn't always mean it was stationary in high water and covered for a period of time.  Cars can be damaged just by driving through high water.  Generally if you suspect a car has been damaged by high water, it should be inspected by a technician and cleaned properly when it concernes the engine, transmission, steering, etc.  Because flooded vehicles are submerged not only in water but in dirt that is suspended in it, which is a terrible combination when it comes to moving parts (i.e. cylinders, pistons, etc).

Some ways you can check a car out if it has been affected by water is by checking the following:

• Check upholstery and carpeting for damage / mildew (particularly the trunk, since there's little air circulating, there will be a musty smell).
• Check how the electrical system works (power door locks, power windows, power seats, cd / radio, speakers all work at the same time, dash lights work evenly at all times, etc) Electrical damage can be very expensive to repare, most sensors are not waterproof.
• Check oil & fluids and see if they look milky or diluted.
• Check headlights for water collection
• Check air filter for moisture
• Check underneath the vehicle for any corosion, rust, debris. (some vehicles from the north will have some rust from the salt on the roads which is normal).

Best way to avoid a problem is to be proactive.  Arm yourself with knowledge before you buy a car.  If in doubt, don't buy it.  If you have to have it, then spend a few dollars and have it professionally inspected, particularly if you're investing several thousands of $ in it or more.