Checking all the electrical wiring and equipment after flooding

Our house was flooded with water due to incessant rain. Water rose to 4 feet level in the house. Many of the plug points were submerged. Water pump and motor etc got submerged.

The house has concealed wiring within the brick walls. The water drained off in less than 24 hours. Can anybody suggest a systematic way to check all the electrical wiring and equipment like pump etc before switching it on again.
A "megger", basically a 500 volt insulation tester is most common for low voltage wiring,

If the cables are water logged they can be dried out under careful supervision with low voltage high amperage power source.

Do not energize before testing, as that is when the damage takes place.