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If the engine died while going through high water and now won't crank then there was most likely water ingested into the engine. Water isn't compressible and if it gets sucked in through the air intake it will cause the engine to hydrolock.
Start by using a socket and ratchet or breaker bar on the crank damper bolt and see if the engine will turn by hand. If it won't turn by hand then you can remove the spark plugs and that will most likely allow it to turn again. You can turn it by hand to expel most of the water and then crank the starter, put the spark plugs back in and see if it will start and how it runs. Since water doesn't compress it will usually damage the engine if it hydrolocks, so you would most likely have some internal engine noise when it is running again. At the least it usually bends the rods.