You have to find your own comfort level. Making the choice not to pursue the sport because it isn't for you can be hard but is the wisest one. You say your class is a weekend course, I'm not so sure that's the best choice for you. I too was an anxious student and the class I took was 10 weeks at the university and I STILL wasn't comfortable enough to pass my OW check-outs the first try. My instructor insisted on an extra day of diving where I was tasked with convincing her I was comfortable in the water. I managed to fake my way through that extra day but it was sheer determination rather than actual comfort. You can see in my logbook where I actually started getting comfortable with my skills and confident I could deal with an emergency if it arose, that was Dive #52 for me.
All I can think is, when the regulator quits or gets knocked out of my mouth, it won't be after I inhaled deeply like we practice in the pool. It will probably be just after I exhaled all the air in my lungs while swimming vigorously, so my body will be using oxygen so rapidly I will have even less time to find the regulator before losing consciousness.
Properly maintained gear generally does not just "quit" mid-dive, if you have that kind of luck you better be playing the lottery because you'll be winning regularly. You have a pressure gauge, just like you have a fuel gauge in your aircraft. Check them both regularly, running out of gas in either is easily prevented. There's no harm in coming back with a lot of air in your tank, there are some really good posts here on the board for calculating "rock bottom" pressure. You should take the time to find and read them and learn to do it.
Having a regulator knocked out of your mouth means 1 of 2 things.
1. You're not aware of what's around you and you got close enough to something to hang your regulator hose in it.
2. Some jerk who was not aware of his surroundings just tangled himself in your regulator hose.
Both situations are pretty easy to deal with. For #1 learn to pay attention to your surroundings. Ever fly lower than the towers around you? You better be paying attention to where they are and aware that there can be guy wires in the area stabilizing them. Same thing with scuba "stay alert, stay alive". Most new diver scuba problems can be prevented with awareness. When you see a problem approaching (tree in the quarry for example) take whatever action is appropriate (stay far enough away to give regulator hose room to pass).
For #2 you may be ticked off enough at the jerk that just landed on you that you take the time to shake your fist at him (and maybe share a few other gestures) before you bother recovering your regulator and muttering into it. I recommend securing your octopus with a necklace instead of the other do-hickeys. (something else to look up)
A necklace leaves your octopus regulator basically right under your chin, no searching for it is necessary if, for some reason you took extra long cursing the clutz who landed on you. You do have to keep in mind that if a diver comes to you out of air you will have to donate the regulator from your mouth instead of your octopus. Some instructors train that way but it's not a big deal to practice that way if you weren't trained that way.
Diving does not generally involve swimming vigorously. The harder you work the faster your air goes and the shorter your dive will be. The goal is to move slowly and enjoy the scenery not race from one part of the site to the other. Think "mosey" and notice the little things on the dive. You don't have to do dives in areas with currents and I would recommend getting comfortable with basic dives in calm water before you decide to take on a site that could require vigorous swimming.
So how am I supposed to deal with a situation when I can't breathe anything and I have limited time in which to act?
You should go through all your options in your head and do practice scenarios regularly. I always tell my students that during the drills if something isn't going right and they don't think they can execute it then STOP, return to a safe configuration underwater and start the drill again. HELLLOOOO, they are DRILLS not real emergencies and you get "DO-OVERS" until you can execute the drill comfortably. The way you train is the way you will dive. Screwing up a drill and moving on to something else increases the odds of screwing the response up when it counts. Divers who take the time to drill, drill, drill until the correct response comes naturally will fall back on their training when the fecal matter hits the blades and may have the problem solved correctly before they even had time to think about the fact they had a problem. You CAN get the correct response into muscle memory and get to a point where you don't have to think about what you would do, you simply act. These skills deteriorate if not used regularly though, that's why it's important to practice basic skills on a regular basis. The safety stop at the end of your dive is a perfect time to practice your basics, you don't have much else to do for 3 minutes.
BTW, had you told me I would be teaching scuba 10 years after I got certified I would have told you that you'd lost your mind. I freaked out about EVERYTHING and drove my instructor crazy...yet here I am, I've been training divers for 5 years now. I tell my students, "You CAN'T freak out about anything I haven't already freaked out about...I have an entire collection of 'been there, freaked about it' shirts."
Ber :lilbunny: