First off, I have no experience with sleeping in any position other than laying down. Here's what happened:

We were standing up doing breathing exercises in band, and we were receiving a long lecture so I just closed my eyes. I stopped thinking about my hands and arms, and they went numb and so did my legs, eventually all I could feel was the weight of my head. Then I was wading up to my chest in water, and a wave came by and I was standing in class again.

It wasn't vivid but it was there. Seems like the most effective way to fall asleep is in class? Why is that/experiences?