If you've ever had a panic attack in your life, you know that they are absolutely awful. While a panic attack on dry land is bad enough, imagine having one while you're scuba diving 50 feet underwater. If you think that sounds harrowing, seeing it happen will make your whole body tense up.
The following video was recorded by a scuba instructor in South Africa last summer. He was out with a group when one student panicked. She spit out her regulator and took off her mask.
Unable to calm her, the instructor initiated an emergency ascent. This girl is lucky to be alive.
After watching that, I feel like I'm seriously on the verge of having a panic attack myself. This is why I don't like to swim (or to be near large bodies of water in general). Excuse me while I kiss the solid ground.