That's really weird when they submerge. I would have thought you'd put a canopy up at first or something. Also, it looks like the breathing apparatus is built into the car?

Yes on both counts. Unlike Bond's vehicle from "The Spy Who Loved Me," this does not have an airtight cabin.

It's probably much safer this way. You can just swim up if there is a problem.

Yes, it appears the air is part of the car. But I imagine that you can easily take the air canister with you for your emergency swim to the surface. That would be an important safety feature.

I like the idea- except the thing looks realllllllllly slow underwater. And the video is fun- except for the obvious implication that the girl gets naked.