I don't tend to get freaked out by anything diving-wise ahead of time, so I guess I am not really "afraid" of anything.
Having said that, I am exceedingly cautious when doing things underwater because I know I am an unskilled NOOB and I understand that doing stupid NOOB stuff can get my buddy or myself injured or dead. On my recent trip, we both declined to do several things like fairly tight swim throughs or going down to a deep level to see a particular creature because it was below our risk/reward threshold (this was going to 90 feet to hang out until the garden eels were up... when I saw they were down and we were at 80, I turned us back because I didn't want to blow through my air that fast)... we had previously done at 112 foot deep dive for AOW training, so this wasn't outside my training... it was just outside where I wanted to go on the dive (even though it was a planned descent).
I am careful and cautious, but I know sooner or later things are going to go wrong... I don't want to get lost at sea so I carried a safety sausage, air horn and whistle on a dive were you really don't need them. I took a spare computer on the dives as backup instrumentation... etc.
Will things happen that I am not expecting... of course they will. Will I be able to handle them? I sure hope so, but I will let you know when/if I get back from the dive...
No need to sit around thinking about stuff to be afraid of, in my NOOB (and therefore unknowing) opinion... instead it's better for me to listen to what everybody else is afraid of/concerned about and figure out what kind of training I need to do moving forward to deal with those problems should they happen to me....
I don't like the sound of those downdraft/updraft problems along a wall at all... and I don't really know what to do if that happens to me... but I am going to find out and train for it.