2012 Prius c flooded help please

How high was the water in the car?

 

Its done for.
Saltwater damage isnt fixable.

 

I'd suggest a look at this thread, where posts 14 and 20 refer you to a Toyota TSB (the number is in post 20) all about quickly classifying your car as to the kinds of consequences you need to check for according to what areas the water occupied.

 

That means the hybrid battery and battery ecu were submerged. The hybrid battery is under the rear seat.

It very likely the can bus is down preventing modules from talking to each other. It would be useful to plug in a good scanner and determine if any of the ecus communicate.

At the minimum you would have to remove any connector or module that was wet, clean it and hope for the best.

 

Any cheaper/faster fix than by following the TSB mentioned in #5 may prove disappointing or worse.

 

^ Yep, and it sounds like your traction pack went under water. So fuses are most likely blown there too along with the emergency safety disconnect. If the traction battery ECU survived. You may want to check what kind of total voltage you've got in the pack, because you won't be able to crank the engine, if that's dead.
Did you change the ATF? There's a vent cap that the salt water can get into, in the upper portions of the transmission. FYI

 

I am afraid the whole experience is disappointing. Having lived near the coast after hurricanes, flooded cars are a problem longterm even if they are made functional again. To replace everything needed for reliability is not economically viable which is the reason insurance, if covered, will total the car.

The tsb is free on the NTSB website:

At minimum, you would have to remove any connector or module that was wet, clean it and hope for the best.

 

There are a bunch of ECUs (don't know the exact count for a c, but probably over a dozen); whichever one you're thinking of as the 'main' one is far from the only one needing attention.