If you sucked mud into the engine it probably chewed up your intake valve and scored the cylinder wall among other things. Or the mud running back down the exhaust could have damaged the exhaust valve when you cranked it over. Could have hydrolocked the engine and damaged all sorts of stuff. If you're truly low on compression after that, there is no quick fix.
Besides that, water anywhere in the ignition coil, wiring, or kill switch will make it not fire.
Your carb bowl is probably full of water
Your carb Jets are probably plugged up with crap from trying to run on water
There's probably water in your oil
Let it dry for a day or two, give it a thorough carb cleaning and an oil change and put a compression tester on it. That will give you a better idea of you damaged the engine itself.