My scariest dive was at the Pangalisang dive site off Bunaken Island, North Sulawesi, Indonesia, because of conditions I wasn't prepared for and mistakes I made. We started our dive site swimming against a medium current along a reef wall, but before long, we couldn't go any further because the current had gotten far too strong. So we turned around and rode the current back, trying not to bump into each other or damage any coral. During the return, my tank came loose from my BCD because I had made the mistake of not double-checking everything after the dive staff had set up our gear. Fortunately, my buddy and the divemaster were able to wrestle my tank back into the band and tighten it.
Then, because I kept bumping into my buddy with the current, I made my next mistake and moved out a bit further from the wall, promptly getting swept outward and away from the group in a stronger, faster part of the current. My first reaction was to kick hard against it to get back to the group; that too was a mistake, because I should have been kicking across the current, not tiring myself out by fighting it.
As I was trying to kick my way free, I felt one of my fins slipping off my boot. I immediately doubled over, grabbed the fin and got it back on, then resumed kicking. I did manage to kick out of the current and back to the group, but at a price: I'd been gulping air as I was fighting the current, and had to end my dive earlier than the others.
In the end, I learned a lot from that dive, my first experience with strong currents. Though my initial reaction in the outward current wasn't the right one, I managed to keep my head and didn't panic, and I knew if I couldn't kick free, I could surface on my own and signal the boat if necessary. I also learned the value of always double-checking my own gear, and carrying signaling gear at all times in case I ever have to surface away from the group. It may not have been the most fun dive I've logged, but it's one I'll remember for a long time.