It probably stalled due to lack of air and or water ingestion. First check the oil for water. It will either be milky or overfull. If this is the case change the oil. If it will not turn over at all pull the plugs and keep turning the motor over until the water is gone. You should disconnect the fuel pump when doing this. Reinstall the plugs and hook back up the fuel pump. It will start unless you fried a fuse or something electrical. I deal with this all the time when boats sink. And once when i tried to use my snowmobile as a boat. but thats another story. Usually the engine shuts down before major damage occurs. Shawn