How do cars drive through deep water as shown on many videos online?

I have read many warnings about driving a car through deep water. Some problems that this can cause is destroy the catalytic converter and in petrol engines water can cause damage to spark plugs. And in diesel cars I thought you needed a special exhaust if you want to drive with the engine underwater. And I also saw a video about a car that had its engine destroyed.

How much of this is true? And how do those 4 wheel drive cars drive with their engines submerged in muddy water ?

I have myself driven a Toyota yaris through water as high as the top of its wheels and nothing happened although I did keep the engine on high revolutions.

What is the recommended thing to do if you need to pass through an area that's been flooded? (Ofcourse the answer will depend on the car)

I have seen many videos and pictures of cars driving through deep water and here are two examples: 1. https://m.youtube.com/watch?v=ednZi2T-TsA&t=58s 2. https://m.youtube.com/watch?v=LC5ld79joIA