Rick Inman:
I think the logic is (and I'm not saying I agree) if you can free-dive down to 30 feet, thats 30' up and 30' down which equals 60'. So if you are on scuba at 60' feet and run out of air, you know you can easily make a free ascent.
Maybe, but it's not quite that simple. When I freedive, I use power (finning) thus oxygen during the first part of the descent, until the point where my wetsuit compresses and I become neutral, then negative, usually around 35' or so. (Someone once compared the sensation to "slipping without falling") Then from there I "slip" to whatever depth I want - no more power (oxygen) usage required until I decide to stop, turn around, or maneuver. Then my next power/oxygen usage occurs on the ascent, to power up off the bottom, which gets easier and easier as the wetsuit and lungs expand and become more buoyant.
Freedivers as a rule are incredibly in tune with their weight (among other things) and I can "set" my weight depending on how deep I plan to go. I typically will never set my weight to make me negative any shallower than 15' though for safety reasons.
Freediving is a blast - I was freediving long before I was certified on scuba. I enjoy visiting scuba divers at depth - I can usually hang around for 15, 20, 30 seconds or so dpending on depth. As a rule I'm not in it for the competition although I did attend the Eastern Regional Championships this spring. I'm a self-coined "underwater tourist" - I go down to explore, to see what's there. I've never tried hunting since spearfishing is illegal in Ontario, but I've swam inside schools of fish (lake perch, mostly) with my (cheap) camera.
Now I have also found that freediving has had a marked effect on my scuba - not only has my air consumption plummeted, but I find myself able to completely relax underawter as well as I have heightened awareness of my environment while diving, compared to how I was as a beginning scuba diver.