Math puzzle.

Unless the oil is saturated with water it likely won’t hurt anything from sitting but anywhere that the water has sorta washed away the oil like in a cylinder will have some degree of rust. Seen some rust bad in a few days and others years later it will scuff off and be fine.
I’d probably let it run a few minutes
30 seconds won’t do anything for drying it.
I know a guy who drove a farm tractor 5 miles to my shop for an overhaul with no water in the cooling system…the radiator wasn’t even on it and really didn’t cause any damage…not sure what the motivation for that stunt was

 

You wouldn't have any issues with the bearings, but you could get some rust on the rings. You may also get quite a bit of rust up top on the jakes, rockers, etc.

While that coolant was getting into the pan, when the engine was hot and ran with water in the oil, you probably noticed what appeared to be excessive blowby.

For the most part, that blow by was steam. All that hot moisture rises, and what doesn't make it out the blowby tube, ends up as the slimey grey mess on the inside of the valve cover, and on the jakes and rockers.

Me personally, if was letting it set till spring. I'd drain the coolant and oil, Spin it over by hand till it turns over easy so you know there is no coolant on the piston. Drop 8 or 9 gallons of diesel in the oil pan and fire it up for 45 seconds or so.

That should clean the top end off very well, remove any moisture from the drain ports and back into the pan, and flush remaining coolant off the piston and rings, while adding some lube to the cylinders.

Obviously oil pressure will be very low. I wouldn't worry about that for just a short run.

 

Running with only diesel for lube oil would scare the shat out of me. It would probably clean the top good if enough actually gets up there in that time

 

I get it. It's definitely unconventional. The oil pump would pick up the diesel in seconds, and be pumping out on top of the head in even less.

It's not something i would do under normal circumstances, but I worry about that moisture setting all winter.

I've seen so many engines run with large amounts of diesel in the oil from failed injectors, that it just wouldn't concern me for a short term start up

 

Some of the same engines wiped out the old bearings too .