I bought a flood damaged vehicle years ago, changed carpet, took sump off, changed ecu( lives on passenger floor) middle eastern bloke was trying to change the amplifier in the boot( thought it was the ecu haha) drained all fluids ie brake, box, diff, engine and drove around for ages never had a problem one of the most reliable cars i've had ( toyota aristo 2jzgte)wasn't listed as a repairable writeoff, the headlight was a clue( half full of water lol) it just depends how deep the water got in and if any mechanical issues, luck of the draw.