Well, how far can YOU swim on one breath?
I know for a fact that my kid could swim the distance between us on one breath.
However, saying that divers should be one breath away is ridiculous! I can swim 100 feet on one breath... Is that at all relevant?
Dive buddies need to be close enough to render effective aid and facilitate communication.
The safe buddy distance is dependent on visibility, currents, relative position and many other parameters but NOT on how far you can swim on one breath, particularly if both divers are equipped with redundant scuba systems.
erm, yours was defective.
Of course the distance between buddies is relevant with regard to how far you can swim on one breath. You go OOA and can't reach your buddy because you are too far away = problem.
You crack on mate, hope you and your son have many great dives together.
I see things I consider not good in the video, you don't. Each to their own