Sump diving in a raging river of runoff no vis with single unmounted tanks and FFMs is nothing like DIR or GUE. It would be criminally negligent to train people in these conditions or even to purport to train them in these conditions. Sump diving is learned from the caving community (which have been doing it a long time) not from the scuba diving community (who you might be shocked to learn are relative newcomers). The rift between caver's way of doing things and the DIR/GUE etc way of doing things goes back 30+ years. There are some highly competent cavers who also happen to swim underwater occasionally. You will almost never hear or see them on a scuba oriented board or in scuba magazines. To them diving is merely a mode of transportation to explore more cave.
Here's a pic of one of my sump dives, note that I'm sidemounting an al27 in a plate-less harness, not wearing a wing, not even wearing fins. I "walked" on the ceiling to pass this flooded section which was about 1m high floor to ceiling. I am Cave1 & Cave2 with GUE but this kind of "diving" is completely outside of their universe. This sump led to about 375m of previously unexplored (dry)passage which we walled out.
EDIT:
This is a timely article. Notice how completely different the training is. No courses at all, dry caver competency first, application to a club, 12 to 18 months apprenticeship.
Meet The British Underground
Which isn't actually all that different than getting involved with cave diving projects. Once you get past the tourist caves whatever cards you have don't matter very much.
I've heard of him doing the odd wreck dive here Perth. But his longest dive is the Pearce Resurgence in New Zealand (17 hours). I'm sure it wasn't done DIW
