But in seriousness hyperoxia is mildly psychedelic, especially when you are in a state (athletic, euphoric, love etc) which naturally produces high levels of serotonin, oxytocin, dopamine, etc.
When I was backpacking for 7 months with my wife, I would climb mountains as fast as I could and wait for her at the tops. I started doing wim hof while waiting and it was deeply rewarding