For me free diving is a spiritual thing. Nowhere else am I more calm, more sure of myself, I can be a visitor to an entirely different world.
What the article doesn't mention is most people can increase their lung capacity using several techniques like over-unders (pool drills where you swim across a pool alternating between underwater and regular),Oxygen tables, breathing patterns (think meditation), and working out while holding your breath (be careful with that one, I'd suggest just walking holding your breath first).
Can you share any good resources for training?
Breathing exercises: http://freedivingexplained.blogspot.com/2008/03/freediving-t...
The "go to" forum for me: https://www.deeperblue.com/
Read some of their literature, the freedivers, participated in some of their training sessions and saw first hand how they have completely mastered their oxygen requirements.
It's quite something to be able to swim unaided for several minutes at a time. Lots of reports of peacefulness and relaxation. The closest I can get is when snorkelling, dipping under for a while. Not a patch, I'm sure.