I just spent about an hour discussing scooter free diving with Kirk Krack of
http://www.performancefreediving.com/ . Kirk has been doing deep scooter free diving well below 50 m for many years. He just did three 90 m (almost 300 ft.) scooter free dives on the Cayman Wall recently.
There are extensive safety and procedural considerations, only some of which are touched upon in the above account. For this reason a warning notice has been added to the start of the post. In short, scooter free diving isn't recommended and certainly not as a casual undertaking with minimal preparation.