Based on Facebook comments, I believe Pete is using video lights and a single exposure. He's swimming around the wreck and placing them while being able to see where the lights goes, then backing up and taking the photo. The key to this is not making a mess while swimming backwards and forwards through your scene! I reckon his great results wouldn't be possible on open circuit with bubbles knocking rust off the roof.
I prefer working with strobes for the increased power output but they can be fiddly to get placed in the right spot. I find co-operative and well-trained buddies to be the best way to position additional strobe lighting through dark places. Placing strobes on the wreck itself is hard work - lots of hot spots and dark spots.
While nowhere near as exciting as Pete's recent shots, here's what I achieved during a week in Truk in January with off-camera strobes on divers: