OK, I am a little confused here. We have many experienced divers ascending two different ways.
A few newbie questions: Which is safer? Which should I practice more? Is one better than the other?
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stakanak: Although I'm in the ascend-using-breath-control-at-near-neutral-buoyancy camp, I can imagine certain situations when it might be prudent to ascend while being slightly negatively buoyant, e.g., buddy forgot to bring enough lead, boat traffic at surface, etc.
No method is 100% "safe." How many times have you found yourself holding your breath during strenuous exertion? If a diver is severely negatively buoyant and kicking hard to ascend, inadvertent breath-holding would increase the possibility of cerebral arterial gas embolism.
I'd recommend trying both methods of ascending to figure out which method feels more comfortable for you. Contrary to what some people might write here on SB, there is no scuba police.
My instructor pointed out that the kicking ascent is used because you always (try to) stay slightly negative which leaves you, not the BC, in ultimate control of your ascent.
That's not a very convincing explanation. First, staying negatively buoyant during an ascent is going to make ascending more of a work-out than it needs to be. It also begs the question how the diver should maintain depth during a safety stop. Is he supposed to kick all of the time? I do longer safety stops and forcing myself to kick for 7-10 minutes straight is kind of ridiculous. Second, buoyant forces play a role during all phases of the dive, including the ascent. The diver is the one responsible for operating his BCD, so there is no abdication of ascent control to the BCD itself. The BCD is just a tool...it's not an unruly beast that you're riding to the surface.
I would have understood if your instructor said that, for newer divers who don't have the best buoyancy control, it might be safer to stay slightly negatively buoyant during the ascent to protect against an uncontrolled ascent. All the diver has to do is stop kicking and he'll sink. But he didn't say that, did he?