Oh man, I wasn't able to grab my regulator a few times (I was able to collect it in my arm, but I didn't realise I did), panicked and after a minute shot up to the surface. This was in a diving pool at just a couple of meters so that was fine, but obviously wouldn't have worked in the ocean once I was at any real depth. I'm very glad I didn't try to touch the instructor, but that moment of sheer panic is real, and it's hard to control your response. It was embarrassing, and I was surprised by my response to it.