10. Accidentally swimming off a waterfall.
Folks were cliff jumping, and to get to the cliff you had to jump across a ~3 foot wide gap across a small creek above a waterfall. I wanted to do it too, but slipped as I jumped and fell in the water. Cue the classic movie scene of me grasping plants and tree roots to stop myself only to have them pull out of the ground. I eventually went off the ~20 foot waterfall, broke my foot somehow on the way down, and felt like a complete idiot for the next several months while I limped around.
