Well, many engines have oil under those covers from hasty oil changers who can't feed the oil slow enough thus spill oil over the edge and it'll pool under that cover. If you're a clean fanatic, it'd be best to remove that cover, degrease the oil from that area but ideally blow dry the water off the top. Then be sure to remove the plug wires from each cyl and blow the water out as some always gets into those holes. I'm assuming that have an air compressor or access to one? If not, I'd use alot of rags or paper towels. Don't drive the car with water in those spark plug holes.
That's about the only thing you need to be concerned with unless your distributor cap and/or wires aren't good and if so, it'll either not start or run poorly.
Water in any electrical connector is never a good thing and that's usually not a problem but it can happen if the engine is washed and if so, the terminals can corrode. Just something to consider.