Is it flooded?
With gas? ;-)
You know the old necessities: Fuel, Air, Spark.
It does sound like something electrical didn't like the water. Did you stick a timing light on the plug wires to see if they're getting any spark? (I'm unfamiliar with the finger/thumb test - is that where the plug wire is disconnected and you hold it ~ 1/2" from ground when you crank the engine?) If they're getting a spark, then either the plugs are fouled or you're not getting fuel in the cylinders. Have you tried a spray of ether?
Otherwise, I dunno, except to say that it'll likely be the last thing you check. So check that last thing next and get it over with. :-)
Good luck.
Cheers,
Scott.
