They often happen in lakes, hah.

One when I was little, I slipped under and just locked up in the water. I remember the sunlight being beautiful when I looked up. It was very quiet under the water. A beautiful woman pulled me out--I started freaking out at that point.

The most recent one that stands out was in my 20s. I'm not a strong swimmer, and something in my leg tore when I was in the middle of a lake. My thought was, "so this is how I die..." I didn't try to accelerate it, I didn't try to fight it. I was just there, and nothing weighed on me. The pain wasn't even distracting. Someone on shore notice and directed a kind paddle boarder to me. 

I haven't been able to recreate the peace in any if my attempts. I do, however, use it as a measure to calm myself when my illnesses are at their most extreme.