You don’t know yet… You have to go a bit further to find out how extensive the damage is.

Where are you at with it / what have you done/checked/tested to this point?

Year/make/model/engine?

Did the previous owner say?
Buying a flooded car without some serious knowledge of what you’re doing is almost certainly going to be a bad time.

You shouldn’t buy flood cars without knowing what you are doing. Ignore engine for now, you might need harnesses and modules, seat frames, cushions carpets etc. once that thing gets warm you going to get mold (health hazard) and smells. And at any point can start getting warning lights and random electric problems. Even seen airbags fail due to corrosion from water.

Now the engine. That can go either way. If the car flooded past the engine height it can fill any cylinder with open valves with ease. Odds are it was running and sucked in intake or through exhaust, incredibly common for people to go into deep water and stall and suck water in exhaust. And the engine is likely toast at that point. If it was deep water you need to worry about transmissions, differentials, transfer cases etc have water in them too.

Buying a car that was in a flood you might as well find a deep river or lake and send it right back in.

Careful with flood damage vehicles some have got sick and even death due to bacteria

If the car was running it could be catastrophic to the engine. (Broken pistons bend connecting rods, corrosion in internal places) So the engine is one thing now let’s look at the wiring harness the seals for the connectors are good but not waterproof so the car may have electrical faults that are hard to track down. And all the mold in the air ducts, carpet, seat foam. Who knows. What kind of car ?