Remove the spark plugs & air filter. Turn over the engine to expel water from the cylinders.

Check the oil level, if it is over the high level there may be a lot of water in the sump so oil & filter will need changing.

Dry out the electrics & plugs & turn over the engine to see if you have sparks.

If ok replace the plugs & see if it will start.

Yeah, but most of them are diesel-probably no valve overlap, and little vacuum in the intake.

Partial vacuum pulses in the exhaust isn't as outlandish as it seems. The effect is used in high performance headers to help scavenge the cylinders. It was also used as a secondary air injection method in the 70s-thus negating the need for an air pump. The exhaust manifold contained valves which would open to quite literally suck air into the exhaust stream.

I wasn't questioning your advice btw. I was just pondering how the water got in!

Sorry, I should have clarified-I meant the intake manifold is under high vacuum when the throttle is closed. The exhaust ports 'see' the vacuum during valve overlap. There is an AVERAGE postive back pressure, but in each exhaust port, the pressure fluctuates above and below atmospheric. Since the exhaust pipe is usually only about 6 inches off the ground, it is easier for water to enter the exhaust-particularly if the vehicle is almost stationary-and there would be little bow wave. The exhaust ports (usually) are also at a much lower height than the intake pipe. Perhaps petrol offroad cars would be better fitted with exhaust snorkels instead of intake snorkels?!

The secondary air injection was used in US cars in the 70s. Federal emissions limits were much stricter than European standards at the time. Electronics were not good enough to operate a 3 way cat. The solution was to run the engine rich to keep NOx levels down. Air was then injected into the exhaust stream by vacuum or via a separate pump to oxidise the HC and CO via a simple oxidation catalyst. You are quite correct-the air did nothing to yield crankshaft torque.

OP-Sorry, this is really off topic. I hope your rods are fine and your car is back on the road!

Excactly-when I was in the business,it was astonishing how many engines "hydrauliced" when driven thro' 1/2" of water at 1 mph!!!