There should be a compression release lever on the engine that will allow it to turn over and pump the water out. You also need to drain you muffler of water. There should be a little brass cap showing at the base of the muffler chamber, loosten it and let it drain.
You must have tried to start the enging and let it crank over to many times without starting, this will fill the muffler up and then it back flows into the motor, (sshhhh been there done that).
Good luck, rookie.