I believe it's hard when the vehicle doesn't have water inside, since you're effectively pushing against the external water pressure. But once the car is full/near-full of water, it becomes much easier — just like opening a door regularly.

They all have mechanical door pulls, it is mandatory.

Yeah, I just talked with a Rivian engineer (who owns a Tesla) and he said that all these vehicles have mechanical pulls, but the problem is that they are hidden and people don't know where they are. It's kind of odd the article didn't mention this fact and enlighten the readers as to how to avoid the same fate!

Here's how to do it in a Model 3. [1] Apparently it differs by vehicle.

1: https://www.youtube.com/watch?v=mu-tJc-BgaI

On the X/Y/3 front doors the pull handles are kind of where you expect it on a normal car, at least the ones I've seen.