Yes, surface supply just for black water. The whole point is you don't know what's down there and surface supply, done properly, gives you a virtually unlimited gas supply. It also removes gas management from the diver, letting him focus on diving.
As has been pointed out prior, it is far more gear and personnel intensive. We need 6 people absolute minimum to put two of them in on surface supply. Longer to set up, much more training needed, but it is really a quantum leap in safety and efficiency (given that most PSD dives are shallow enough to not need tables, you can work for hours and hours). You also have the most trouble free coms system you can have.
I've penetrated into some overhead environments, once in true black coffee water, that I simply would not have done without surface air.
We only go scuba/aga with a 100 or 80 plus a pony on a hard line coms tether when its essentially a bounce dive to an already located and roughly identified target.