That all depends on how high the water got. If it was high enough to enter the intake, that's bad. Also remember your TOD module and most sensors are below that level as well as the ECM and transmission, transfer case and differential breathers. The other factor is how long was it flooded and how long has it been since it was flooded and what was done immediately after to help mitigate the damages. It's always a gamble to buy flood damaged vehicles. There's a darn good reason why insurance companies total 'em even though they may look undamaged...