i hydrolocked my car today while driving in a flood.

can trying to start the car while hydrolocked damage the car?

Is there an alternative fix besides replacing the engine?

IF you hydrolocked it , it is too late.

I guess there's a chance the engine is still usable. You'll need to pull all the spark plugs and probably drop the exhaust at the manifolds. Pull the fuses for the fuel pump and the ignition coil. Then see if the engine will crank over freely and without a lot of noise. You can use the starter, but I'd suggest you try with a long bar and socket on the crankshaft pulley first. If you're able to turn the engine over without a whole heck of a lot of resistance, then drain the engine oil out, drop the oil filter, install a new oil filter, and fill the crankcase with inexpensive oil. Crank the engine over a few times, this time trying the starter. Again, if it cranks over without a lot of noises then you can try installing the spark plugs again. Put the fuel pump and ignition coil fuses back in and see if it will start. You may need to cycle the key a few times to get the fuel system pressurized again.

-Rod

If he got some water in the engine it may be salvageable.

If he actually Hyrolocked the engine he bent a rod, busted a piston, bent a valve, or at the very least busted the piston rings.