There are many out there that believe that 02 is at LEAST as narcotic as nitrogen- if not more. Since your body is using it up as you breath it you run into other problems- like inner ear DCS.
I've never freedove on it, but I do use 02 to clean myself out after a very long day in the water- like up at Freedive-a-palooza where I am in the water for over 10 hours at a time. The 02 at the end of the day helps me to stay awake long enough to eat my dinner.
I use a bottle of pure 02 and just hang out on the fish cribs at 20' for about 10 minutes or so after my last freedive of the day.
For normally long days in the water, like spearing, I don't use anything except a cup of coffee if I have a long drive home.
Jon
