Watery oil spot

It would be pretty tough for water to "splash" its way into an oil pan. Maybe if the oil filler cap was off and the hood was open with a big funnel... more likely splashed rain water washed accumulated oil and grease off the engine as it was parked. But to know for certain you'll have to check the oil in the pan for signs of water contamination, and check the coolant for signs of oil contamination. If you have either, it's more likely you have a blown head gasket - of course you would see other signs of a bad engine if that were the case. You're doing the right thing, taking it in for a checkup.