I’m a little surprised this thread had gone on this long without a reference to Hal Watts, aka Mr SCUBA. Perhaps he was more of a local legend of cave and deep diving from the 60s and 70s.
FWIW, I had my first training in ‘90 and Hal was credited with the “invention” of the octopus.
This is no doubt another case of recurrent and concurrent discovery. Adding another single hose second stage hardly raises to the level of invention. Divers figured out that you could add another second stage as soon as first stages with extra ports hit the market. It appears that there were a few isolated cave divers with a highly inflated opinion of themselves and very little curiosity about what was happening around the world in the diving industry.
I am reasonably sure that cave divers first invented or used the line reels constantly.
Reels were widely used by scientific divers and for search and recovery in the 1950s. A really well made, and expensive, cast aluminum model was sold in the back pages of Skin Diver in the 1960s. The concept of stringing guidelines inside wrecks goes back to surface supplied heavy gear divers in the late 1800s.