[djtango]

For sure - what I find interesting is that passing out is a disqualification (I assume) so there is a fine line between achieving your utmost limit and being disqualified. Which is like most sports but my understanding is that it is quite easy to accidentally slip under so the guy must have incredible body awareness

[Azrael3000]

Correct. Usually you need to perform a so called surface protocol after surfacing to show you are still conscious enough. This can be e.g. the removal of your mask, an OK sign and saying "I'm OK". Only if you do that within 15 seconds after surfacing your performance will be valid.

And regarding easy to blackout. Yes and no, I personally avoided it for over 12 years, but then again, I'm no world class athlete and only an enthusiastic hobbyist.