Well......
[Insert standard boilerplate condemnation of solo freediving here]
I once made the following observation, which I've not had the chance to explore more fully since then:
I had spent 4-5 hours as a support freediver for some people training for world record attempts. I was in 88 degree (F) water for about 3 of those hours, mostly floating, but did perhaps 20 dives to exactly 20 meters ( my safety station for the athletes' training dives) each lasting between 1:30 and 2:15 ( this according to the logged data in my Mares apneist computer). These were slow, easy dives. There were no incidents requiring my intervention, no emergencies. Some of the dives were to check or replace the colored depth markers at the 20m point on the descent lines. Mostly I pulled mself down the line, very little kicking ( being the lazy bastard I am).
About 2 hours after the dive boat had returned and docked, after the training session, the athletes, trainers and support crew were in a hotel pool giving a lecture and demonstration on static apnea technique to an audience of local freedivers. I was in the pool as a part of the audience, really, just doing what the audience was doing. Near the end of the lecture, the trainer called for the audience to go for a maximum static apnea attempt.
To my astonishment, I easily passed my then-personal-best, and a while later got nudged up to finish by my buddy who wanted to get out of the pool and join the others who were already sitting on the deck ordering cocktails. It was a long one, and I was not at the end of my rope at all.
The theory I contrived from this experience is this: maybe the best warmup for static apnea is not static apnea, per se, but exosure to hydrostatic pressure. Perhaps the ideal scenario for attempting personal bests or world records in static apnea would be a warmup consisting of 10 - 20 no-effort (free immersion, or even a method using weights to pull you down and a lanyard to pull you up) descents to 20-30 meters, followed by a rest period of an hour or so, followed by 2 warmup statics in the nearby pool ( say, to 1/3 and then 2/3 of your target time with 5-10 minute vents in between) followed by the target dive.
I'm just guessing about the specifics here - but I am very intrigued by the idea of using exposure to depth as a warmup for static apnea on the surface. One can speculate as to the reasons it seemed so effective to me - blood shunt comes quickly to mind. As far as I know, none of the top static apnea contenders have tried it, but I hope to persuade one of them ( who shall for the moment remain nameless) to explore it with me in the near future. Watch Deeper Blue for news !
Paul