As someone who lost their car to flooding last year I thought that I would pass along some information. This was complied from multiple sources and Facebook posts found online.

Before you start your car there are certain steps you should take to prevent hydro-locking your engine and thus totaling your car.

To prevent hydro-locking your car, take notice of the following things First and act accordingly with your vehicle.

1. Mark the high water line on the outside of the driver door. Use tape or a permanent market. You can tell where the high water line is or was from the debris sticking to the side of your car. This way your insurance company can document the depth of water your car was under.
2. As a general rule if water got into your car and covered the seats (usually 6-8 inches of water) your car will be declared a total loss by the insurance company. This happens because there are a lot of electronics in the floor board of your car and water damages and causes them to corrode quickly overtime instead of operating for its full intended lifespan. The electrical wiring would need to be completely replaced for functionality and reliability to be restored. It costs more to replace all wiring in a car than to replace the entire car so insurance companies declare cars total losses and replace them.
3. Checking the air filter located under your hood can help you determine if you can start your car safely. If the filter is wet or appears to have gotten wet it is an indication that your engine has water in it. If you try to start your car when water is in the engine you will destroy it.
4. Check your oil dipstick as well to determine the state of your car. If it appears to have a lot of oil in it (the dipstick oil level reads very high) it means that your engine has water in it. If you try to start your car you will destroy it.
5. If the oil level appears to be normal then proceed with caution and only turn your ignition so the battery will engage. Do not fully try to start your car yet. If the battery is dead and your dashboard doesn’t light up do not try to start the engine. This means that something electrical has shorted out and your battery has drained. If you try to jump the vehicle you will only worsen the problem.
6. If your dashboard lights up and your battery seems to be operational then you may have lucked out. You may now try to start the vehicle. If you hear a click and the engine doesn’t turn over stop trying to start the car. You will do more damage if you keep trying to start the car. A mechanic will need to address this problem if it doesn’t start the first time.
7. If the engine turns over but doesn’t start, stop trying to start the car. There is probably an electronic issue or computer issue. Unfortunately this probably means your vehicle will also be a total loss. You will need to proceed with a professional mechanic evaluation and report it to your insurance.
8. If the engine starts, let it run for about a minute and then turn it off. There are still a few things to check. Do not rev the accelerator.
9. Open the hood and find the oil dipstick again. Get a piece of white paper and let the dipstick drip oil onto it. If it is a clear, brown or black there is no water in your oil. If the oil appears to have water drops in it or looks like chocolate milk you have water in your oil and the oil will need to be drained and replaced. Have your car towed to a local repair shop. If you choose to drive it there yourself you are risking destroying your car.
   
10. If the oil appears to have no water in it then it is time to pull your transmission dipstick. Use another piece of white paper and drip transmission fluid on it. If it is a translucent clear, red or reddish brown it is normal. If it looks like strawberry milk or has clear droplets in it then you have water in your transmission. Have your car towed to a local repair shop. If you choose to drive it you are risking destroying your car.
11. If both sets of fluids seem clear there are a few more things to check. Go ahead and start your engine and turn on your Air Conditioning and let your car idle for about 5 minutes. Check the cooling fans in the front of your car on the radiator. If they are not spinning, do not drive the car because it will overheat. Have it towed to a repair shop to have the fans replaced.
12. If everything looks good then your car is most likely in decent condition and was not heavily affected by the flood. You should still take it to a local mechanic and have the entire vehicle rechecked to ensure no damage occurred that is detrimental to its operation.