The most likely area of a problem is the ignition system.
Even thought the distributor cap is sealed you still have to consider that getting water over the cap itself and onto the outside of the cap, the hi tension ( spark plug and coil wires) , even down to the wire areas that lead to the spark plugs themselves. Also consider the nice steam bath that everything in the engine compartment received as that steaming water sizzled off of the exhaust manifold and pipes.
If you let it sit for a few minutes the heat off the engine probably dryed things off, and then it started up, made more heat and then continued to dry things up for you. When you have 25,000 - 35,000 volts on the secondary system, it still will always look for the path of least resistance and the water provides the path.
The other problem to consider is condensation within the distributor and the inside of the distributor cap itself. Take a nice warm surface inside of the cap, and distrubutor, suddenly chill the outside down, ( like the spashing water) , and you now have condensation inside the cap etc. Also remember that as the secondary voltage travels down the wrong path, whether it is inside the cap, the spark plug boot, or even down the outside of the spark plug insulator, it will likely leave a permanent carbon path. It will look just like someone used a pencil and drew a line on the surface. Once its there it is almost always permanent.
The best way to stop all of this from occuring is prevention. ( now I sound like a doctor). Best thing would be to keep the water from spashing onto the ignition system, ie splash shields etc. Next would be to have good quality plug wires cap rotor etc. that have nice tight water sealed connections. Keep a can of W.D. 40 handy, as the water dispersent ( that why they call it W.D.) qualities are very good.
It is a good idea to occasionally spray the plug wires near the spark plugs, and the distribitor cap area, and then blow off the excess with compressed air. Next time you sink the engine in water, give it a few minutes to let the the water drip off, and the engine heat to help dry things up. Opening the hood would help to let the water and steam escape. Remove the dirtibutor cap, spray the inside of the cap, rotor etc, and then use compressed air or a rag to mop up the excess WD40. Spray the wires, and especially the area when the water works it way down to like the area near the spark plugs. Try and remove the excess W.D. 40 after spraying, and this will take away the water too.
A couple of additional tips that I have seen that work. One time when I was at a mud race ( that had serveral deep water holes) I watched as a mother that ended up selling an entire box of clean huggies for $5.00 each. You can laugh at this , but a huggie wrappped around the vulnerable distributor cap provided a water proof insulator, that has some velco that made it fit almost any distrubutor cap around! Another couple of improvements is electric coolong fans instead of the water pump driven fan that does sprays water all over the place as you are revving that engine up, and the fan is spraying water all over the engine. Distrutorless ignitions ($$$) with individual coils are another luxury the ends the problem of water condensation in the cap.
Sorry for the typo errors, as I have to head off to work.
Just remember, if you play hard, you pay.
