My friend dove into a shallow pool when we were younger and broke the atlas bone in his neck. It was very scary. He had to have surgery and wore a special neck brace for a while after that.
Whenever he talks about it, he always calls it a Jefferson fracture. I assume that it is a special term for that type of break, but I'm not certain. I'd be interested to know where the name originated.
If a pool has a "No diving" sign posted, there is a reason. It's for everyone's safety.