There are more-and-more articles about solo diving in open water. It surprises me since we are taught about the absoluteness of the buddy system. What is your opinion on it, and under what conditions would you consider diving solo?
Solo diving has been going on for as long as there has been diving. So why doesn't PADI have a solo diving course? Safety and commitment. PADI recognizes solo diving at the Public Safety and Technical level. As a Tech Instructor I can get a Distinctive Specialty from PADI to teach a solo diving course. But PADI knows that to do a safe solo dive requires a level of commitment from the diver that many sport divers are not willing to give.
Solo diving does not mean you do not have a buddy, it means you are your own buddy. All agencies teach redundancy in solo diving. On a sport dive your buddy brings another source of air that you can use if you run out. He brings another set of eyes should you lose your mask. He brings another brain should yours go on vacation during the dive.
To do a proper solo dive you should have a completely redundant air supply. Not just an octopus but a pony bottle with regulator. If you run out of air at depth what do you think you'll get if you start sucking on your octopus? Right, nothing. You need a totally separate source of breathing gas to safely ascend.
if you lose your mask you won't have a buddy to safely guide you to the surface. You need to carry a spare mask in a pocket easy to locate and to access. And you better be really good at breathing without a mask and with mask replacement underwater. Oh yeah, buoyancy control. You wouldn't want to sink too deep or rise to fast while replacing your lost mask with your backup.
Your buddy can't loan you an extra brain whenever you go diving (actually, I've seen some divers in the water I would swear had left their brains at home). So you have to plan your dive, double check you plan, dive your plan, and not be afraid to call a dive if anything goes wrong. Even little things if there is enough of them. Thise that have dove with me, especially cave or tech diving, know I have a "Three strikes and you're out" rule. Three things go wrong and it's time to call the dive. Even if I'm not in the water yet. Get to the water's edge and find I left my mask in the car, that's one. Not enough weight and get more, that's two. Drop my fin and have to hunt for it, that's three. Time to get out of the water, even if for only 5 minutes. Reboot my brain and start again. It doesn't mean my diving is done for the day, only that I need to start over. If you read an accident report there always seem to be a number of little things that went wrong during the dive. None were major but they added up to enough stress on the diver to result in a problem. Solo diving requires your brain be fully engaged and as stress free as possible.
And yes, I am writing a Solo Diver course for training at the store.