It's very peculiar that nowhere in the discussion here or Chamberland's video does anyone mention NOAA's Aquarius habitat, in operation since 1988: http://www.uncw.edu/aquarius/ . Aquarius has been in operation as a civilian research station underwater off Key Largo for years. Before that it was in the Virgin Islands. It is operated by NOAA (the National Oceanic and Atmospheric Administration) for marine biology research and NASA training. It's an amazing place where researchers get to do 10-day research projects that would be difficult or impossible to run from the surface.
But what's not mentioned by Chamberland or anyone involved in his little promo piece is that living underwater is grueling. You're in a single-wide trailer equivalent with multiple other people. Going outside is wonderfully liberating, but y'know, it's cold. Even in Florida, once you've been in the water for a few hours, you're cold. Then you do it again. And again. It's humid and pretty much everyone gets skin problems after a few days.
And you can't come up. You've saturated to 55-foot depth after a day, so you'd get the bends if you surfaced. So all your diving is done with cave-diving rigs that are designed for diving where there's no surface to go to. If you get in trouble, you have to get back to the habitat, not the surface. Oh, you'd probably survive if you had to surface, but it wouldn't be healthy or pretty. At the end of the 10-day mission it takes 18 hours to decompress to surface pressure.
That said, it is really truly astounding to live underwater for a while. Looking out through the window at dinner at the fish, and realizing that they're looking at you: you're the one in the aquarium. It's a trip.
But it's an incredibly resource-intensive thing to do. Rough estimates I recall from my Aquarius trips were that it cost about US$10,000 per day to support four researchers in the habitat. That's not sustainable for daily life.
As far as I can tell, Dennis Chamberland wants to set up some sort of high-end hotel-like underwater facility. More power to him. But don't pretend that we're all going to have the chance to go live under the ocean.