Pull the spark plugs, crank the engine, change any fluid that has water in it. You likely have water in the engine oil. I'd also check the transmission fluid. If it spent much time sitting in water, check the differential fluid. You probably need to change the air filter. Hydro locking an engine can bend/break connecting rods and valves. A bent valve stem can cause the piston to hit the valve breaking the valve and/or piston top. When you start the engine listen for expensive noises.
Keep in mind that free advice can frequently be worth less than you pay for it.