A world record free dive occurred in this blue hole in May 2007. William Trubridge of New Zealand made it to 83 m or 273 ft. without fins, weights or pulling down a descent line. He just moved past Martin Stepanek's record of 81 m set two years ago in 2005.
Martin coming up in yet another discipline constant ballast, into a Czech documentary
I recently took a freediving course with Martin, lots of interesting new and good ideas on how to do something that has been second nature for a very long time. The first morning in the pool, guys were holding their breaths for over 3 minutes (static apnea). One new student recently, just a regular guy to look at him with no unusual background (shoots fish?) held his breath for 5 minutes and 20 seconds just by following the techniques Martin described. A few others in that class went over 4 minutes I recall. This is static apnea, or floating face down in a pool motionless not swimming.
It involves a lot more than simply increasing your breath hold duration, there is also a lot of training on recognizing problems in yourself and buddy like shallow water blackout and how to avoid it and response should signs appear. When you push out the envelop it is good to have modified procedures to help see you back to the surface. Martin's ideas take a lot of the randomness out of passing out or not on extended freedives.