Whenever it rains a lot here in Seattle, we tend to have a lot of "urban flooding." Clogged storm drains, temporary construction routes that flood, major highways that look like lakes... you get the idea.
Whenever that happens, we encourage you to NOT drive through standing water. Ever. Because you never know how deep it really is. Or whats under that water. Or etc. etc. etc.
And here is some video proof to back that up (which is what the driver should have done).
The description of the video says this: "This is a view from my D-TEG dashcam. I approached a flooded road and made a quick U-turn rather than driving into the water. This was a naturally smart move. Unfortunately my turn resulted in me plunging off a hidden embankment and splashing nose-first right into a swollen creek where I sunk straight to the bottom, I traveled several hundred feet underwater with the car quickly filling up. At one point I was completely surrounded by water and just holding my breath in the darkness. Somehow the driver-side and passenger-side windows broke and I was flushed from the vehicle. I surfaced after a bit and found myself racing down the creek. A cop called out to me and I was able to swim to him and his life-saving grab."
Even if you're familiar with the area where you are driving, its not a good idea to drive through standing water. If you end up causing massive splashes, you could blinding other drivers and causing a wreck. Or you can drive into a hole that you didn't know was there... like this guy:
We rest our case. Drive safe!