3rd death this year.

Every time someone croaks ab diving people feel the need to post and point out all the wrong things that the deceased or his partner possibly did wrong.

Pilots do the same thing every time someone crashes.  Although I see your point, there's nothing wrong with learning from real-world events.

Nate：
I was trying to point out that it is not safe just to see buddy surfaces but need to wait certain period after buddy finish recovery breath and give okay sign. What you mentioned is exactly what I intend to bring up. Thanks for gave a more detail info including the correct time to wait and the percentage of black outs happen on surface.
Btw, I took the course in Monterey with PFI as well. I also find the difficult to practice the safety protocol learned from PFI in low visibility condition.

In some cases, freediver blacks out after surfacing and take one recovery breath. There was one student blackout in this way in the freediving course I attended and got recovered by his buddy who kept close watching on him. It is better to watch buddy take a few recovery breath and give ok sign (i will say at least 15 seconds) before next dive.

It should be uncommon for spearfishing or abdiving since most ppl won't push limit in this kind of case but I would take caution since body condition changes from day to day and dive to dive.

My reply is not meant to correct your post as I don't know with which company you took your class.  But a class with the Performance Freediving International (school) we were told that 30 seconds was the length of time we should wait for our buddies to give us the "OK" sign.  We were also given a statistic that 90% of BOs occur on the surface.  

I don't know about categorizing blackouts (BO) in spearfishing and abdiving as uncommon.  Though BOs are more common in the sport of freediving, it is far less likely that divers die practicing that sport because the dive buddies are more knowledgeable and are usually solely focused on their dive buddy.  

Most spearfishermen/ab divers will usually not intentionally push their limits but there are times when we extend ourselves as we're trying to pry that ab from the back of a long cave or untangle that tied up fish in a cave or out of kelp.  If we BO, chances are slim that our buddy will see us and come to the rescue.  As hunters we're usually busy with our own patch of the reef or whatever.  And in the relative poor vis. of the North Coast it'd be very hard to see each other even if we were in close proximity.  

I don't have solutions to all the dangers but I try to dive within my limits.  I dive with guys that are much better divers.  I call for them to spot me if I'm working on a tied up fish.  When I feel like I'm Superman and I'm diving "the best I'ver ever dove", then I pay special attention an stick to a very conservative dive profile or get out of the water altogether.  It's when I feel invincible that I know I'm at the most risk.  

Condolences to the deceased diver's family and friends.  

Nate