Oh my....well, start with Freds Guide, make sure you have spark, fuel, and compression.
Spark and Fuel can be affected by water, you might have to dismount the carb and clean/flush it, and if your luck is really bad, some water got down into the cylinder or crank arm.
Best hope not, but start with the carb, cause it's likely you have water contamination in there.
And umm..when checking for spark? holding on to a wet spark plug while cranking is generally a BAD idea - tho you will KNOW if you have spark, that's fer sure - at that point.