2009 Mercedes Benz C300 My car is flooded

First of all, open the doors to let the fish out. Next, if this was salt water, flush the interior out with a garden hose. Wiring, ground connections, seat frames and mechanical parts, and things like that aren't made to resist corrosion from salt and water. Use fans to dry the interior as quickly as possible to prevent mold growth. Remove a few trim panels and the carpet to see if there are plastic or rubber plugs in the floor. Pop those out to let the water drain out.

To do engine damage the water is going to have to reach the air filter. If the engine was not running at the time, water likely didn't get into the engine if it didn't get above the seats. A bigger concern is the wiring. Connectors are sealed and will effectively keep rain out of the terminals, but with prolonged exposure, water could still sneak in. In the future, if you have intermittent electrical problems, corroded terminals in electrical connectors will be a better suspect than normal.