Normal trucks can wade water as high as their air intake, which usually is above one of the front wheels, inside the fender. You can go a bit above that for short distances if you keep a good momentum and create a wave in front of you, but that's risky.

Of course modern trucks, having turned from work to luxury vehicles, may have issues.

The lower the mass sits, the better the truck handles.
If you have something heavy (like a battery pack) which you need to include in the design somewhere, putting it as low to the ground as safely possible is the right choice. So that's not a stupid decision at all. It's what literally all EV makers do because it's objectively the right way to place the battery pack.

Watching that clip, I don't see the typical signs of a battery fire. So I guess, wade mode did in fact keep the battery dry. Wading through a stream reaching to the top of the wheels would probably work fine. But if you stay in the water, it eventually gets through to some electronics and power is cut off by the overcurrent protection. So just don't do that.

The way the vehicle is tilted on one side it definitely went over that. Crazy they decided to take it in there, and that far.

Yeah, I mean why not make a normal truck design with the battery in the cargo area?

The reflecting pool in DC is 18-30 inches, so give it six months and the Diapered Dipshit will probably use it for a Cyberdumpster wading experience once Elon gives him a few mil to advertise it.

Rules out lakes.