mga sir's i have a 1988 nissan california, was submerged in almost waist deep water. It is now starting up and running well , actually better. Here's what i have done;

1. When the waters receded I removed the battery terminals, and checked the dipstick for water intrusion. No water so in engine, whew!

2. I did not start the car. I had it towed to a gas station. Oil was checked, turns out there was a little amount of water in with the oil.
Engine was flushed and oil was changed, while started to clean the interior. Sparkplugs were cleaned, Distributor cap was dried, and the car started after the oil change.

3.I had the interior professionally cleaned/detailed. Better have it done by the pros.

hope this helps